SCHEDULE 13D/A 0001952901 XXXXXXXX LIVE 26 Common Shares 03/11/2026 false 0000912958 L6388F110 MILLICOM INTERNATIONAL CELLULAR SA

8400 NW 36th Street Suite 530 Doral FL 33166

Denis Klimentchenko 44(0)20 7519 7289 Skadden, Arps, Slate, Meagher & Flom (UK) LLP, 22 Bishopsgate London X0 EC2N 4BQ 0001952901 N Atlas Investissement SAS b OO N I0 0.00 73820018.00 0.00 73820018.00 73820018.00 N 44.1 CO (1) Reflects 70,470,018 common shares, par value $1.50 per share ("Common Shares") of Millicom International Cellular S.A., a Luxembourg company (the "Issuer"), beneficially owned by Atlas Investissement SAS, a company incorporated under French law as a societe par actions simplifiee ("Atlas Investissement"), plus 3,350,000 Common Shares that Atlas Investissement expects to purchase under the Equity Derivative Transaction Agreements (as defined in Item 4 below) on or before June 30, 2026. Iliad Holding SAS ("Iliad Holding"), as the controlling shareholder of Atlas Investissement, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement. Maya SAS ("Maya"), as the controlling shareholder of Iliad Holding, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Iliad Holding and Atlas Investissement. Xavier Niel, the President of Maya, Jules Niel, John Niel, Elisa Niel and Joseph Niel (together, the "Niel Family") may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement, Iliad Holding and Maya. (2) The percentage reflected in row 13 in the table above is calculated on the basis of 167,540,829 Common Shares outstanding as of February 28, 2026 (169,000,000 Common Shares outstanding, less 1,459,171 Common Shares held in treasury), as set forth in the last relevant update available on the date hereof on the Issuer's website. Y Iliad Holding SAS b OO N I0 0.00 73820018.00 0.00 73820018.00 73820018.00 N 44.1 CO (1) Reflects 70,470,018 Common Shares beneficially owned by Atlas Investissement, plus 3,350,000 Common Shares that Atlas Investissement expects to purchase under the Equity Derivative Transaction Agreements on or before June 30, 2026. Iliad Holding, as the controlling shareholder of Atlas Investissement, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement. Maya, as the controlling shareholder of Iliad Holding, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Iliad Holding and Atlas Investissement. The Niel Family may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement, Iliad Holding and Maya. (2) The percentage reflected in row 13 in the table above is calculated on the basis of 167,540,829 Common Shares outstanding as of February 28, 2026 (169,000,000 Common Shares outstanding, less 1,459,171 Common Shares held in treasury), as set forth in the last relevant update available on the date hereof on the Issuer's website. Y Maya SAS b OO N I0 0.00 73820018.00 0.00 73820018.00 73820018.00 N 44.1 CO (1) Reflects 70,470,018 Common Shares beneficially owned by Atlas Investissement, plus 3,350,000 Common Shares that Atlas Investissement expects to purchase under the Equity Derivative Transaction Agreements on or before June 30, 2026. Iliad Holding, as the controlling shareholder of Atlas Investissement, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement. Maya, as the controlling shareholder of Iliad Holding, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Iliad Holding and Atlas Investissement. The Niel Family may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement, Iliad Holding and Maya. (2) The percentage reflected in row 13 in the table above is calculated on the basis of 167,540,829 Common Shares outstanding as of February 28, 2026 (169,000,000 Common Shares outstanding, less 1,459,171 Common Shares held in treasury), as set forth in the last relevant update available on the date hereof on the Issuer's website. Y Xavier Niel b OO N I0 0.00 73820018.00 0.00 73820018.00 73820018.00 N 44.1 IN (1) Reflects 70,470,018 Common Shares beneficially owned by Atlas Investissement, plus 3,350,000 Common Shares that Atlas Investissement expects to purchase under the Equity Derivative Transaction Agreements on or before June 30, 2026. Iliad Holding, as the controlling shareholder of Atlas Investissement, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement. Maya, as the controlling shareholder of Iliad Holding, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Iliad Holding and Atlas Investissement. The Niel Family may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement, Iliad Holding and Maya. (2) The percentage reflected in row 13 in the table above is calculated on the basis of 167,540,829 Common Shares outstanding as of February 28, 2026 (169,000,000 Common Shares outstanding, less 1,459,171 Common Shares held in treasury), as set forth in the last relevant update available on the date hereof on the Issuer's website. Y Jules Niel b OO N I0 0.00 73820018.00 0.00 73820018.00 73820018.00 N 44.1 IN (1) Reflects 70,470,018 Common Shares beneficially owned by Atlas Investissement, plus 3,350,000 Common Shares that Atlas Investissement expects to purchase under the Equity Derivative Transaction Agreements on or before June 30, 2026. Iliad Holding, as the controlling shareholder of Atlas Investissement, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement. Maya, as the controlling shareholder of Iliad Holding, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Iliad Holding and Atlas Investissement. The Niel Family may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement, Iliad Holding and Maya. (2) The percentage reflected in row 13 in the table above is calculated on the basis of 167,540,829 Common Shares outstanding as of February 28, 2026 (169,000,000 Common Shares outstanding, less 1,459,171 Common Shares held in treasury), as set forth in the last relevant update available on the date hereof on the Issuer's website. Y John Niel b OO N I0 0.00 73820018.00 0.00 73820018.00 73820018.00 N 44.1 IN (1) Reflects 70,470,018 Common Shares beneficially owned by Atlas Investissement, plus 3,350,000 Common Shares that Atlas Investissement expects to purchase under the Equity Derivative Transaction Agreements on or before June 30, 2026. Iliad Holding, as the controlling shareholder of Atlas Investissement, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement. Maya, as the controlling shareholder of Iliad Holding, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Iliad Holding and Atlas Investissement. The Niel Family may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement, Iliad Holding and Maya. (2) The percentage reflected in row 13 in the table above is calculated on the basis of 167,540,829 Common Shares outstanding as of February 28, 2026 (169,000,000 Common Shares outstanding, less 1,459,171 Common Shares held in treasury), as set forth in the last relevant update available on the date hereof on the Issuer's website. Y Elisa Niel b OO N I0 0.00 73820018.00 0.00 73820018.00 73820018.00 N 44.1 IN (1) Reflects 70,470,018 Common Shares beneficially owned by Atlas Investissement, plus 3,350,000 Common Shares that Atlas Investissement expects to purchase under the Equity Derivative Transaction Agreements on or before June 30, 2026. Iliad Holding, as the controlling shareholder of Atlas Investissement, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement. Maya, as the controlling shareholder of Iliad Holding, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Iliad Holding and Atlas Investissement. The Niel Family may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement, Iliad Holding and Maya. (2) The percentage reflected in row 13 in the table above is calculated on the basis of 167,540,829 Common Shares outstanding as of February 28, 2026 (169,000,000 Common Shares outstanding, less 1,459,171 Common Shares held in treasury), as set forth in the last relevant update available on the date hereof on the Issuer's website. Y Joseph Niel b OO N I0 0.00 73820018.00 0.00 73820018.00 73820018.00 N 44.1 IN (1) Reflects 70,470,018 Common Shares beneficially owned by Atlas Investissement, plus 3,350,000 Common Shares that Atlas Investissement expects to purchase under the Equity Derivative Transaction Agreements on or before June 30, 2026. Iliad Holding, as the controlling shareholder of Atlas Investissement, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement. Maya, as the controlling shareholder of Iliad Holding, may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Iliad Holding and Atlas Investissement. The Niel Family may be deemed to have shared beneficial ownership over the Common Shares beneficially owned by Atlas Investissement, Iliad Holding and Maya. (2) The percentage reflected in row 13 in the table above is calculated on the basis of 167,540,829 Common Shares outstanding as of February 28, 2026 (169,000,000 Common Shares outstanding, less 1,459,171 Common Shares held in treasury), as set forth in the last relevant update available on the date hereof on the Issuer's website. Common Shares MILLICOM INTERNATIONAL CELLULAR SA 8400 NW 36th Street Suite 530 Doral FL 33166 This Amendment No. 26 ("Amendment No. 26") to Schedule 13D relates to the Common Shares, par value $1.50 per share (the "Common Shares"), of Millicom International Cellular S.A., a Luxembourg company ("Issuer"), and amends and supplements the initial statement on Schedule 13D filed on February 24, 2023, as previously amended (as so amended, the "Schedule 13D"). Capitalized terms used but not defined in this Amendment No. 26 shall have the same meanings ascribed to them in the Schedule 13D. Item 4 of the Schedule 13D is hereby amended and supplemented by adding the following: The Equity Derivative Transaction (as defined in Item 4 below) is expected to be funded either with the proceeds to be drawn further to an amendment with a view to upsizing the equity financing transaction with four unaffiliated third party financial institutions, as previously disclosed in Amendment No. 24 to the Schedule 13D, or by funds borrowed from one of the affiliates of Atlas Investissement. Item 4 of the Schedule 13D is hereby amended and supplemented by adding the following: On March 11, 2026, Atlas Investissement entered into an equity derivative transaction (the "Equity Derivative Transaction" and the documentation relating thereto the "Equity Derivative Transaction Agreements") with an unaffiliated third party financial institution (the "Bank"), pursuant to which Atlas Investissement expects to purchase up to 3,350,000 Common Shares on or before June 30, 2026. The actual timing and the number of Common Shares under such transaction will be determined based on the hedging position of the Bank in accordance with certain parameters of the Equity Derivative Transaction Agreements. Under the terms of the Equity Derivative Transaction Agreements, absent any extraordinary event, Atlas Investissement will be obligated to pay the Bank in cash an amount defined under such agreements for the acquisition of a number of Common Shares determined in accordance with the terms of such agreements, in consideration of which the Bank will be obligated, at each relevant settlement date in accordance with the terms of such agreements, to deliver such number of such Common Shares. Cash dividends (relating to the Common Shares not having yet been delivered to Atlas Investissement under the Equity Derivative Transaction Agreements) paid during the term thereof will give rise to a payment by the Bank to Atlas Investissement for an amount determined (taking into account all relevant withholding taxes) in accordance with the Equity Derivative Transaction Agreements. All balances will be exclusively physically settled, absent any extraordinary event, at the scheduled settlement dates of the Equity Derivative Transaction Agreements, although Atlas Investissement has the right to request an earlier settlement date for a physical settlement relating to the entirety of the Bank's hedging position at the relevant time. The Equity Derivative Transaction Agreements provide that Atlas Investissement does not have any direct or indirect voting, investment or dispositive control over any of the Common Shares held by the Bank corresponding to its hedging position until a settlement and delivery of such shares to Atlas Investissement and that the Bank will not notify or consult with Atlas Investissement regarding any voting rights with respect to the Common Shares that relate to its hedging position. The foregoing description of the Equity Derivative Transaction is qualified in its entirety by reference to the terms of the Confirmation relating to the Equity Derivative Transaction, a copy of which is filed as exhibit to this Amendment No. 26 and incorporated herein by reference. See Items 11 and 13 of each of the cover pages. See Items 7 through 10 of each of the cover pages. Except as described in Item 4 above, the Reporting Persons have not effected any transactions in Common Shares since Amendment No. 25 to the Schedule 13D was filed on February 12, 2026. Item 6 of the Schedule 13D is hereby amended and supplemented as follows: The information set forth in Item 4 of this Amendment No. 26 is incorporated herein by reference. Item 7 of the Schedule 13D is hereby amended by adding the following exhibits: 44. Confirmation related to the Equity Derivative Transaction Agreements, dated March 11, 2026, by and between Atlas Investissement SAS and Societe Generale Atlas Investissement SAS /s/ Anthony Maarek 03/13/2026 Iliad Holding SAS /s/ Xavier Niel 03/13/2026 Maya SAS /s/ Xavier Niel 03/13/2026 Xavier Niel /s/ Xavier Niel 03/13/2026 Jules Niel /s/ Jules Niel 03/13/2026 John Niel /s/ John Niel 03/13/2026 Elisa Niel /s/ Xavier Niel 03/13/2026 Joseph Niel /s/ Xavier Niel 03/13/2026