<PAGE>

                                                                  Exhibit 10(ff)

                             AMENDMENT TO AGREEMENT
                              OF PURCHASE AND SALE

     THIS AMENDMENT (this "Amendment"), dated as of April 13, 2000, is by and
                           ---------
among TeleManagement Services, Inc. (the "Company"), Lee H. Edelstein (the
"Shareholder") and TLM Holdings Corp. (the "Purchaser").

                                   WITNESSETH

     WHEREAS, the Purchaser, the Shareholder and the Company have entered into
that certain Agreement of Purchase and Sale dated as of January 1, 1997 (the
"Purchase Agreement"); and

     WHEREAS, the Company was voluntarily dissolved on December 9, 1997, and the
Shareholder, as sole director at the time, is empowered to execute this
Amendment as Trustee of the dissolved corporation; and

     WHEREAS, the parties hereto desire to amend the Purchase Agreement.

     NOW, THEREFORE, for good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged by each of the Purchaser, the
Shareholder and the Company, the Purchase Agreement is hereby amended as
follows:

                                  DEFINITIONS

     Definitions.  Unless otherwise defined herein, capitalized terms used in
     -----------
this Amendment have the meanings provided in the Purchase Agreement.

                                   AMENDMENTS

     1.  Amendment to Section I(D).  Section I(D) of the Purchase Agreement is
         -------------------------
amended and restated in its entirety to read as follows:

     D.  Contingent Payments.    Subject to the conditions set forth herein and
         -------------------
     in Schedule IV hereto, within ninety (90) days after December 31, 1997, and
     December 31, 1998, and within one hundred fifty (150) days after December
     31, 1999, the Purchaser shall deliver to the Company the Contingent
     Payments, if any, payable with respect to the twelve-month periods ending
     December 31, 1997, December 31, 1998, and December 31, 1999, respectively.
     The amount of the Contingent Payments payable to the Company  with respect
     to each such twelve-month period (each, a "Contingent Period") shall be
     calculated based upon the earnings before interest, taxes and amortization
     ("EBITA") achieved by the Contingent Payment Business (as hereinafter
     defined) during such Contingent Period.  Each of the Contingent Payments,
     if any, shall be made by delivery to the Company of (i) a certified or
     official bank check payable to the order of the Company and (ii) a
     certificate representing shares of common stock, $.01 par value ("Purchaser
<PAGE>

                                                                  Exhibit 10(ff)

     Common Stock"), of the Purchaser, registered in the name of the Company, in
     each case, in such amounts of cash and in such numbers of shares as are
     determined in accordance with Schedule IV hereto.  Notwithstanding the
     foregoing or any other provisions of this Agreement (including, without
     limitation, Schedule IV hereto), the Contingent Payment due with respect to
     the twelve-month period ending December 31, 1999:  (a) shall not exceed a
     total of $1.2 million; and (b) shall be paid one-half in the common stock
     of the Purchaser and one-half in cash.

     2.  Amendment to Schedule IV(3).  Section (3) of Schedule IV of the
         ---------------------------
Purchase Agreement is amended and restated in its entirety to read as follows:

     (3)  For the Contingent Period Ending December 31, 1999 the Company shall
          --------------------------------------------------------------------
          receive Contingent Payments equal to:
          ------------------------------------

     The EBITA of the Contingent Payment Business for such Contingent Period
          multiplied by 1.8333 minus the Subtrahend; provided that, in no event,
                                                     --------
          shall the Contingent Payment for such Contingent Period exceed a total
          of $1.2 million.

     3.  Amendment to Payments section of Schedule IV.  The Payments section of
         --------------------------------------------       --------
Schedule IV is amended and restated in its entirety to read as follows:

                                    Payments
                                    --------

     The Contingent Payments will be payable 50% in cash and 50% in shares of
     the Purchaser Common Stock (valued at the lesser of $15.00 per share or the
     Market Price per share (as hereinafter defined) of the Purchaser Common
     Stock).  The term "Market Price" shall mean the average for the sixty days
     ending five business days prior to the date each Contingent Payment is due
     (ninety days after the last day of the prior calendar year) of the last
     sale price regular way, or, in case no sale takes place on any such day,
     the average of the closing bid and asked prices regular way, in either case
     on the principal national securities exchange on which the Purchaser Common
     Stock is listed or admitted to trading, or if the Purchaser Common Stock is
     not listed or admitted to trading on any national securities exchange, the
     last sale price reported on the National Market System of the National
     Association of Securities Dealers Automated Quotation System ("NASDAQ"), or
     the last sale price in the over-the-counter market reported on NASDAQ,
     whichever is applicable, or if there are no such prices reported on NASDAQ,
     as furnished to the Purchaser by any New York Stock Exchange member
     selected from time to time by the Purchaser for such purposes.  If the
     Purchaser Common Stock is not traded on a stock exchange or in the over-
     the-counter market, the Market Price shall be the value of the Purchaser
     Common Stock determined by a New York Stock Exchange member selected by the
     Purchaser and approved by the Company; it being understood that Lehman
     Brothers, Inc., J.P. Morgan & Co., Inc., and Smith Barney Inc., shall be
     deemed to have been approved by the Company to determine the Market Price
     if the Purchaser Common Stock is not traded on a stock exchange or in the
     over-the-counter market.  In the event a Reorganization shall have
     occurred, the "Market Price" per share

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<PAGE>
                                                                  Exhibit 10(ff)

     shall be the value of the Reorganization Consideration per share, with any
     securities included in the Reorganization Consideration valued as set forth
     above and the value of any other non-cash consideration determined in
     accordance with the immediately preceding sentence.

                                 MISCELLANEOUS

     1.  Condition Precedent.  The execution of this Amendment is a condition
         -------------------
precedent to the effectiveness of that certain Amendment Agreement and Waiver to
be executed in connection with that certain Credit Agreement among Access
Worldwide Communications, Inc. (the "Borrower"), certain subsidiaries of the
Borrower, including the Purchaser and the Company, Bank of America, N.A., as
agent, and the lenders party thereto dated as of March 12, 1999.

     2.  Representations and Warranties of the Purchaser and the Company.  Each
         ---------------------------------------------------------------
of the Purchaser and the Company  hereby represents and warrants that each:  (i)
has the requisite corporate power and authority to execute, deliver and perform
this Amendment, as applicable; and (ii) is duly authorized to, and has been
authorized by all necessary corporate action, to execute, deliver and perform
this Amendment, and this Amendment does not violate any law, rule, regulation,
contract or agreement otherwise enforceable by or against either of the
Purchaser or the Company.

3.   Representations of the Shareholder.  The Shareholder hereby represents and
     ----------------------------------
     warrants that he:  (i) has had the opportunity to obtain the assistance of
     legal counsel in carefully reviewing, discussing and considering all terms
     of this Amendment;  (ii) executes this Amendment as a free and voluntary
     act, without any duress, coercion or undue influence exerted by or on
     behalf of any other party;  and (iii) has full and complete authorization
     and power to execute this Amendment in the capacities herein stated, and
     this Amendment does not violate any law, rule, regulation, contract or
     agreement otherwise enforceable by or against him.

  4.                  Limited Modification.  Except as specifically amended
                      --------------------
hereby, the Purchase Agreement shall remain in full force and effect in
accordance with its terms.

5.   No Oral Agreements.  This Amendment may not be contradicted by evidence of
     ------------------
     prior, contemporaneous or subsequent oral agreements among the parties.
     There are no unwritten agreements among the Purchaser, the Company and the
     Shareholder.

6.   Counterparts.  This Amendment may be executed by the parties hereto in
     ------------
     several counterparts (including facsimile counterparts), each of which
     shall be deemed to be an original and all of which shall constitute
     together but one and the same agreement.  Delivery of an executed
     counterpart of this Amendment by telecopy shall be effective as an original
     and shall constitute a representation that an original shall be delivered.

7.   Governing Law.  THIS AMENDMENT AND THE RIGHTS AND OBLIGATIONS OF THE
     -------------
     PARTIES HEREUNDER SHALL BE GOVERNED BY AND

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<PAGE>
                                                                  Exhibit 10(ff)

     CONSTRUED AND INTERPRETED IN ACCORDANCE WITH THE LAWS OF THE STATE OF
     FLORIDA.

  8. Successors and Assigns.  This Amendment shall be binding
     ----------------------
upon and inure to the benefit of the parties hereto and their respective
successors and assigns.

  IN WITNESS WHEREOF, TLM Holding Corp., TeleManagement Services, Inc. and Lee
H. Edelstein have caused this Amendment to be duly executed on the date first
above written.



                              TLM HOLDINGS, CORP.

                              By:_______________________________
                              Name:
                              Title:


                              TELEMANAGEMENT SERVICES, INC.

                              By:_______________________________
                              Name:
                              Title:



   ________________    (SEAL)
  Witness                          Lee H. Edelstein

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