UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             Washington, D.C. 20549

                                  SCHEDULE 13D/A

                    UNDER THE SECURITIES EXCHANGE ACT OF 1934

                                (AMENDMENT NO. 4)

                  PRIMUS TELECOMMUNICATIONS GROUP, INCORPORATED
                                (Name of Issuer)

                     COMMON STOCK, $0.01 PAR VALUE PER SHARE
                         (Title of Class of Securities)

                                   741929 10 3
                                 (CUSIP Number)

                               Sean O'Sullivan RLT
                      6800 West Gate Blvd, Ste 132, PMB #123
                               Austin, Texas 78745
                                 (512) 698-9600
                  (Name, Address and Telephone Number of Person
                Authorized to Receive Notices and Communications)

                                 12 December 2006
             (Date of Event which Requires Filing of this Statement)

If the filing person has previously filed a statement on Schedule 13G to report
the acquisition which is the subject of this Schedule 13D, and is filing this
Schedule because of Sections 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check
the following box. [__]

Note: Schedules filed in paper format shall include a signed original and five
copies of the Schedule, including all Exhibits. See Section 240.13d-7(b) for
other parties to whom copies are to be sent.

CUSIP No.

741929 10 3
- --------------------------------------------------------------------------------
1.    Names of Reporting Persons.
      I.R.S. Identification Nos. of above persons (entities only).

      Sean O'Sullivan
- --------------------------------------------------------------------------------
2.    Check the Appropriate Box if a Member of a Group (See Instructions)
      (a)   [ ]
      (b)   [X]
- --------------------------------------------------------------------------------
3.    SEC Use Only
- --------------------------------------------------------------------------------
4.    Source of Funds (See Instructions)
      PF
- --------------------------------------------------------------------------------
5.    Check box if disclosure of legal proceedings is required pursuant to
      Item 2(d) or 2(e)  [ ]
- --------------------------------------------------------------------------------
6.    Citizenship or Place of Organization

      UNITED STATES
- --------------------------------------------------------------------------------

- --------------------------------------------------------------------------------
                  7.    Sole Voting Power
Number of               12,728,057 shares of common stock, par value $0.01 per
Shares                  share
Beneficially      --------------------------------------------------------------
Owned by          8.    Shared Voting Power
Each              --------------------------------------------------------------
Reporting         9.    Sole Dispositive Power
Person With             12,728,057 shares of common stock, par value $0.01 per
                        share
                  --------------------------------------------------------------
                  10.   Shared Dispositive Power
- --------------------------------------------------------------------------------
11.   Aggregate Amount Beneficially Owned by Each Reporting Person
      12,728,057 shares of common stock, par value $0.01 per share
- --------------------------------------------------------------------------------
12.   Check box if the Aggregate Amount in Row (11) Excludes Certain Shares
      (See Instructions)  [ ]
- --------------------------------------------------------------------------------
13.   Percent of Class Represented by Amount in Row (11)
      11.2%
- --------------------------------------------------------------------------------
14.   Type of Reporting Person (See Instructions)
      IN
- --------------------------------------------------------------------------------


ITEM 1. SECURITY AND ISSUER

This constitutes Amendment No. 4 (the "Amendment") to the Statement on Schedule
13D, dated March 23, 2006, relating to sales of shares of common stock, par
value $0.01 per share (the "Common Stock") of Primus Telecommunications Group,
Incorporated, a Delaware corporation (the "Issuer"). The address of the
principal executive offices of the Issuer is 7901 Jones Branch Drive, Suite 900,
McLean, Virginia 22102.

ITEM 2. IDENTITY AND BACKGROUND

(a) through (f):

      This Amendment is being filed on behalf of the following natural person
      (the "Filer"): Sean O'Sullivan, as Trustee for the Sean O'Sullivan
      Revocable Living Trust, also known as Sean O'Sullivan RLT.  Mr. O'Sullivan
      is a self-employed engineer and entrepreneur who from time to time makes
      purchases in public and private entities. His principal business
      address is 6800 West Gate Blvd, Ste 132, PMB #123, Austin, Texas 78745.

      The Filer has not (i) been convicted in a criminal proceeding or
      (ii) been a party to a civil proceeding of a judicial or administrative
      body of competent jurisdiction and as a result of such proceeding has
      been or is subject to a judgment, decree or final order enjoining future
      violations of, or prohibiting or mandating activities subject to,
      federal or state securities laws or finding any violation with respect
      to such laws.

      The Filer is a citizen of the United States and additionally is a
      citizen of Ireland.

ITEM 3. SOURCE AND AMOUNT OF FUNDS OR OTHER CONSIDERATION.

Reference is made to the Schedule 13D dated March 13, 2006, Amendment #1 dated
July 27th, 2006, Amendment #2 dated August 4th, 2006, and Amendment #3 dated
November 17th, 2006.  There have been no material changes to such information
except as set forth below.

On December 8th, 2006, the Filer made an open-market purchase of 1,700 shares
of PRTL from cash funds for a price of $716.00, or $0.41 per share.

On December 12th, 2006, the Filer made an open-market purchase of 5,000 shares
of PRTL from cash funds for a price of $2,055, or $0.41 per share.

On December 13th, 2006, the Filer made an open-market purchase of 5,000 shares
of PRTL from cash funds for a price of $1,900, or $0.38 per share.

On November 28th, 2006, the Filer made an open-market purchase of 600 shares
of PRTL from cash funds for a price of $275, or $0.40 per share.

ITEM 4. PURPOSE OF TRANSACTION.

Filer acquired the securities reported herein for investment purposes and may,
from time to time, depending on such Investor's evaluation of the market for
the Common Stock, other opportunities available to it, its financial
requirements and other possible future developments, decide to increase or
decrease its holdings of the Common Stock.

Except as otherwise set forth in this Item 4, the Filer has no present
plans or proposals which relate to or would result in:

            (i)   the acquisition by any person of additional securities of the
                  Issuer, or the disposition of securities of the Issuer;

            (ii)  an extraordinary corporate transaction, such as a merger,
                  reorganization or liquidation, involving the Issuer or any of
                  its subsidiaries;

            (iii) a sale or transfer of a material amount of assets of the
                  Issuer or any of its subsidiaries;

            (iv)  any change in the present Board of Directors or management of
                  the Issuer, including any plans or proposals to change the
                  number or term of directors or to fill any existing vacancies
                  on the Board of Directors;

            (v)   any material change in the present capitalization or dividend
                  policy of the Issuer;

            (vi)  any other material change in the Issuer's business or
                  corporate structure;

            (vii) changes in the Issuer's Certificate of Incorporation, By-laws
                  or instruments corresponding thereto or other actions which
                  may impede the acquisition of control of the Issuer by any
                  person;

            (viii) causing a class of securities of the Issuer to cease to be
                  quoted on The Nasdaq Stock Market, Inc.

            (ix)  a class of equity securities of the Issuer becoming eligible
                  for termination of registration pursuant to Section 12(g)(4)
                  of the Exchange Act; or

            (x)   any action similar to any of those enumerated above.

ITEM 5. INTEREST IN SECURITIES OF THE ISSUER.

(a) and (b):

      The information required by these paragraphs is set forth in Items 7
      through 11 and 13 of each of the cover pages of this document.

      Such information is based upon 113,809,000 shares of common stock
      outstanding as of June 30, 2006, as indicated in an SEC filing
      from the Issuer.

(c):

      There were no additional transactions by the Filer with respect to the
      Issuer other than those described in response to Item 3 hereof.

(d) and (e):

      Not applicable.

ITEM 6. CONTRACTS, ARRANGEMENTS, UNDERSTANDINGS OR RELATIONSHIPS WITH RESPECT
TO SECURITIES OF THE ISSUER.

Except as otherwise set forth in this Filing and the Exhibits filed herewith,
there are no contracts, arrangements, understandings or relationships between
any of the Filers or any of the Covered Persons and any other person with
respect to any securities of the Issuer, including any contract, arrangement,
understanding or relationship concerning the transfer or the voting of any
securities of the Issuer, finder's fees, joint ventures, loan or option
arrangements, puts or calls, guarantees of profits, division of profits or
loss, or the giving or withholding of proxies.

ITEM 7. MATERIAL TO BE FILED AS EXHIBITS.

There are no written agreements between the Filer and the Issuer relating
to the filing of joint acquisition statements as required by Section
240.13d-1(k) and there are no written agreements, contracts, arrangements,
understandings, plans or proposals relating to:  (1) the borrowing of funds
to finance the acquisition as disclosed in Item 3; (2) the acquisition
of issuer control, liquidation, sale of assets, merger, or change in business
or corporate structure or any other matter as disclosed in Item 4; and (3)
the transfer or voting of the securities, finder's fees, joint ventures,
options, puts, calls, guarantees of loans, guarantees against loss or of
profit, or the giving or withholding of any proxy as disclosed in Item 6.

                                    SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify
that the information set forth in this statement is true, complete and correct.

Date: August 14, 2006                    SEAN O'SULLIVAN RLT

                                        By:     /s/ Sean O'Sullivan
                                            ---------------------------
                                            Name: Sean O'Sullivan
                                            Title: Trustee