<PAGE>   1

                                                                  EXHIBIT 10.25

                               FIRST AMENDMENT TO
                                CREDIT AGREEMENT

         THIS FIRST AMENDMENT TO CREDIT AGREEMENT ("Amendment") is made and
entered into as of the 1st day of March, 1997, among BILLING INFORMATION
CONCEPTS, INC., a Delaware corporation ("Borrower" ); BILLING INFORMATION
CONCEPTS CORP., a Delaware corporation ("Parent Company"); ENHANCED SERVICES
BILLING, INC., a Delaware corporation ("ESBI") (Parent Company and ESBI,
collectively, the "Guarantors"); and THE FROST NATIONAL BANK, a national
banking association, individually, as the Issuing Bank and as the Agent, THE
BOATMEN'S NATIONAL BANK OF ST. LOUIS, a national banking association,
individually, and each of the lenders which becomes a party to the Credit
Agreement as provided in Section 10.7 thereof (individually, a "Bank" and
collectively, the "Banks").

                                    RECITALS

         A. Borrower, Parent Company, the Agent, the Issuing Bank and the Banks
have heretofore entered into the Credit Agreement dated as of December 20, 1996
(as amended, modified, restated and supplemented from time to time, the "Credit
Agreement").

         B. Borrower, Parent Company and the Banks desire to amend the Credit
Agreement to increase the amount which Borrower may loan to its customers
pursuant to Advanced Payment Agreements.

                                   AGREEMENTS

         NOW, THEREFORE, in consideration of the premises and mutual covenants
herein contained, and for other good, fair and valuable considerations, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree that the terms and provisions of the Original Credit Agreement are
amended and restated as follows:

         1. Defined Terms and Related Matters.

            (a) Unless otherwise defined herein, the capitalized terms used
         herein which are defined in the Credit Agreement shall have the
         meanings specified therein.

            (b) The words "hereof", "herein" and "hereunder" and words of
         similar import when used in this Amendment shall refer to this
         Amendment as a whole and not to any particular provision of this
         Amendment.

         2. Amendments. Section 6.5(viii) of the Credit Agreement is hereby
            amended to read in its entirety as follows:


<PAGE>   2


                 "(viii) loans to customers of Borrower in the ordinary course
            of business other than pursuant to Advanced Payment Agreements not
            exceeding $1,000,000 in the aggregate at any time; and"


         3. In order to induce the Agent, the Issuing Bank and the Banks to
enter into this Amendment, Borrower and Parent Company hereby represent and
warrant to the Agent, the Issuing Bank and the Banks that, as of the date of
this Amendment, (a) the representations and warranties set forth in the Credit
Agreement and each other Loan Document to which it is a party are true and
correct as if made on and as of the date hereof (other than those
representations and warranties expressly limited by their terms to a specific
date), (b) no Default or Event of Default has occurred and is continuing, and
(c) no event has occurred since the date of the most recent financial
statements delivered pursuant to Section 5.1 of the Credit Agreement that has
caused a Material Adverse Effect.

         4. Borrower hereby acknowledges and agrees that no facts, events,
status or conditions presently exist which, either now or with the passage of
time or the giving of notice or both, presently constitute a basis for any
claim or cause of action against any of the Banks, or any defense to the
payment of any of the indebtedness evidenced or to be evidenced by any of the
Loan Documents.

         5. ESBI covenants and agrees that, as to the Affiliate Guaranty
executed and delivered by ESBI in favor of the Banks as part of the Security
Documents, such Affiliate Guaranty is a continuing guarantee and shall remain
in full force and effect until the termination of the obligations of the Banks
to make Loans or issue Letters of Credit and the indefeasible payment in full
of the Obligations (as defined in such Affiliate Guaranty).

         6. Parent Company covenants and agrees that, as to the Parent Guaranty
executed and delivered by Parent Company in favor of the Banks as part of the
Security Documents, such Parent Guaranty is a continuing guarantee and shall
remain in full force and effect until the termination of the obligations of the
Banks to make Loans or issue Letters of Credit and the indefeasible payment in
full of the Obligations (as defined in such Parent Guaranty).

         7. As to each Security Document executed in favor of the Banks,
Borrower hereby ratifies and confirms the liens and security interests of the
Banks in and to all collateral covered by each such Security Document to which
Borrower is a party as security for the prompt and full payment and performance
of the obligations secured by each such Security Document. In furtherance of
the foregoing, all liens and security interests of each such Security Document
(which are hereby acknowledged to be valid and subsisting) are hereby carried
forward, continued, extended, modified and renewed to secure the prompt and
full payment and performance of the obligations secured by each such Security
Document.

                                      -2-

<PAGE>   3


         8. Each Loan Document is hereby amended and modified to the extent
necessary to give full force and effect to the terms of this Amendment, and
each such Loan Document shall hereafter be construed and interpreted after
giving full force and effect to the terms of this Amendment. As amended,
modified and supplemented pursuant to this Amendment, Borrower, Parent Company
and ESBI hereby ratify, confirm and restate each Loan Document to which it is a
party and agrees that each such Loan Document shall continue in full force and
effect. Each of the Loan Documents now or hereafter executed and delivered
pursuant to the terms hereof or pursuant to the terms of the Credit Agreement,
as amended hereby, or as further evidence of or security for or in connection
with the Credit Agreement, as amended hereby, is hereby amended to the extent
necessary so that any reference in any such documents, instruments or
agreements to the Credit Agreement shall be a reference to the Credit
Agreement, as amended hereby.

         9. In the event that any one or more of the provisions contained in
this Amendment shall be determined invalid, illegal or unenforceable in any
respect for any reason, the validity, legality and enforceability of any such
provision or provisions in every other respect and the remaining provisions of
this Amendment shall not be impaired in any way.

         10. When required or implied by the context used, defined terms used
herein shall include the plural as well as the singular, and vice versa.

         11. This Amendment shall be governed by and construed in accordance
with the internal laws of the State of Texas and applicable federal laws of the
United States of America. This Amendment has been entered into in Bexar County,
Texas and shall be performable for all purposes in Bexar County, Texas. The
courts within the State of Texas shall have jurisdiction over any and all
disputes arising under or pertaining to this Amendment; and any such dispute
shall be heard in the county or judicial district of the principal place of
business of The Frost National Bank.

         12. This Amendment shall be binding upon and inure to the benefit of
all parties hereto and their respective successors and assigns; provided,
however, that neither Borrower nor Parent Company nor ESBI nor any of their
respective successors or assigns may, without the prior written consent of all
of the Banks, assign any rights, powers, duties or obligations hereunder.

         13. This Amendment may be executed in any number of counterparts and
by different parties hereto on separate counterparts, each of which when so
executed shall be deemed to be an original and all of which when taken together
shall constitute but one and the same instrument.

         14. This Amendment constitutes a Loan Document.

         15. Upon execution of this Amendment by the Banks, Borrower, Parent
Company and ESBI shall deliver to the Agent, in form and substance satisfactory
to the Agent, the certificates and documents described on Annex A.

                           [signatures on next page]

                                      -3-

<PAGE>   4


         IN WITNESS WHEREOF, the parties hereto have caused this Amendment to
be duly executed by their respective authorized signatories as of the day and
year first above written.

                                  BORROWER:

                                  BILLING INFORMATION CONCEPTS, INC.


                                  By:         /s/ Kelly E. Simmons
                                     ------------------------------------------
                                  Name:       Kelly E. Simmons
                                       ----------------------------------------
                                  Title:      Senior Vice President and CFO
                                        ---------------------------------------

                                  PARENT COMPANY:

                                  BILLING INFORMATION CONCEPTS CORP.


                                  By:         /s/ Kelly E. Simmons
                                     ------------------------------------------
                                  Name:       Kelly E. Simmons
                                       ----------------------------------------
                                  Title:      Senior Vice President and CFO


                                  GUARANTORS:

                                  ENHANCES SERVICES BILLING, INC.



                                  By:         /s/ Kelly E. Simmons
                                     ------------------------------------------
                                  Name:       Kelly E. Simmons
                                       ----------------------------------------
                                  Title:      Senior Vice President and CFO
                                        ---------------------------------------

                                  BILLING INFORMATION CONCEPTS CORP.


                                  By:         /s/ Kelly E. Simmons
                                     ------------------------------------------
                                  Name:       Kelly E. Simmons
                                       ----------------------------------------
                                  Title:      Senior Vice President and CFO
                                        ---------------------------------------

                    [signatures continued on following page]

                                      -4-

<PAGE>   5


                                       BANKS:

                                       THE FROST NATIONAL BANK
                                       Individually, as the Issuing Bank and as
                                       the Agent


                                       By:        /s/ Gregg M. Chinn
                                          -------------------------------------
                                       Name:      Gregg M. Chinn 
                                            -----------------------------------
                                       Title:     Vice President
                                             ----------------------------------

                                       THE BOATMEN'S NATIONAL BANK OF ST. LOUIS


                                       By:        /s/ Steven A. Linton
                                          -------------------------------------
                                       Name:      Steven A. Linton
                                            -----------------------------------
                                       Title:     Assistant Vice President  
                                             ----------------------------------

                                      -5-
<PAGE>   6

                              SECOND AMENDMENT TO
                                CREDIT AGREEMENT

         THIS SECOND AMENDMENT TO CREDIT AGREEMENT (this "Second Amendment") is
made and entered into as of the 29th day of September, 1998, among BILLING
CONCEPTS, INC., a Delaware corporation, formerly known as BILLING INFORMATION
CONCEPTS, INC. ("Borrower"); BILLING CONCEPTS CORP., a Delaware corporation,
formerly known as BILLING INFORMATION CONCEPTS CORP. ("Parent Company");
ENHANCED SERVICES BILLING, INC., a Delaware corporation ("ESBI"); BILLING
CONCEPTS SYSTEMS, INC., a Delaware corporation, formerly known as COMPUTER
RESOURCES MANAGEMENT, INC. ("BCSI") (Parent Company, ESBI and BCSI,
collectively, the "Guarantors"); and THE FROST NATIONAL BANK, a national
banking association, individually, as the Issuing Bank and as the Agent,
NATIONSBANK, N.A., a national banking association, successor to THE BOATMEN'S
NATIONAL BANK OF ST. LOUIS, individually, and each of the lenders which becomes
a party to the Credit Agreement as provided in Section 10.7 thereof
(individually, a "Bank" and collectively, the "Banks").

                                    RECITALS

         A. Borrower, Parent Company, the Agent, the Issuing Bank and the Banks
have heretofore entered into the Credit Agreement dated as of December 20, 1996
(as amended, modified, restated and supplemented from time to time, the "Credit
Agreement").

         B. Borrower, Parent Company and the Banks desire to amend the Credit
Agreement to increase the maximum amounts of Consolidated Capital Expenditures
permitted during the Fiscal Years ending September 30, 1998 and thereafter.

                                   AGREEMENTS

         NOW, THEREFORE, in consideration of the premises and mutual covenants
herein contained, and for other good, fair and valuable considerations, the
receipt and sufficiency of which are hereby acknowledged, the parties hereto
agree that the terms and provisions of the Credit Agreement are amended and
restated as follows:

         1. Defined Terms and Related Matters.

            (a) Unless otherwise defined herein, the capitalized terms used
         herein which are defined in the Credit Agreement shall have the
         meanings specified therein.

            (b) The words "hereof", "herein" and "hereunder" and words of
         similar import when used in this Second Amendment shall refer to this
         Second Amendment as a whole and not to any particular provision of
         this Second Amendment.

         2. Amendments. Section 6.1(c) of the Credit Agreement is hereby
amended to read in its entirety as follows:

                "(c) Consolidated Capital Expenditures to exceed (i)
            $20,000,000 for the Fiscal Year ending September 30, 1997, (ii)
            $10,000,000 for the Fiscal Year ending September 30, 1998, (iii)
            $15,000,000 for the Fiscal Year ending September 30, 1999 or (iv)
            $5,000,000 for any Fiscal Year ending September 30, 2000 or
            thereafter."


<PAGE>   7


         3. In order to induce the Agent, the Issuing Bank and the Banks to
enter into this Second Amendment, Borrower and Parent Company hereby represent
and warrant to the Agent, the Issuing Bank and the Banks that, as of the date
of this Second Amendment, (a) the representations and warranties set forth in
the Credit Agreement and each other Loan Document to which it is a party are
true and correct as if made on and as of the date hereof (other than those
representations and warranties expressly limited by their terms to a specific
date), (b) no Default or Event of Default has occurred and is continuing, and
(c) no event has occurred since the date of the most recent financial
statements delivered pursuant to Section 5.1 of the Credit Agreement that has
caused a Material Adverse Effect.

         4. Borrower hereby acknowledges and agrees that no facts, events,
status or conditions presently exist which, either now or with the passage of
time or the giving of notice or both, presently constitute a basis for any
claim or cause of action against any of the Banks, or any defense to the
payment of any of the indebtedness evidenced or to be evidenced by any of the
Loan Documents.

         5. ESBI covenants and agrees that, as to the Affiliate Guaranty
executed and delivered by ESBI in favor of the Banks as part of the Security
Documents, such Affiliate Guaranty is a continuing guarantee and shall remain
in full force and effect until the termination of the obligations of the Banks
to make Loans or issue Letters of Credit and the indefeasible payment in full
of the Obligations (as defined in such Affiliate Guaranty).

         6. BCSI covenants and agrees that, as to the Affiliate Guaranty
executed and delivered by BCSI in favor of the Banks as part of the Security
Documents, such Affiliate Guaranty is a continuing guarantee and shall remain
in full force and effect until the termination of the obligations of the Banks
to make Loans or issue Letters of Credit and the indefeasible payment in full
of the Obligations (as defined in such Affiliate Guaranty).

         7. Parent Company covenants and agrees that, as to the Parent Guaranty
executed and delivered by Parent Company in favor of the Banks as part of the
Security Documents, such Parent Guaranty is a continuing guarantee and shall
remain in full force and effect until the termination of the obligations of the
Banks to make Loans or issue Letters of Credit and the indefeasible payment in
full of the Obligations (as defined in such Parent Guaranty).

         8. As to each Security Document executed in favor of the Banks,
Borrower hereby ratifies and confirms the liens and security interests of the
Banks in and to all collateral covered by each such Security Document to which
Borrower is a party as security for the prompt and full payment and performance
of the obligations secured by each such Security Document. In furtherance of
the foregoing, all liens and security interests of each such Security Document
(which are hereby acknowledged to be valid and subsisting) are hereby carried
forward, continued, extended, modified and renewed to secure the prompt and
full payment and performance of the obligations secured by each such Security
Document.

         9. Each Loan Document is hereby amended and modified to the extent
necessary to give full force and effect to the terms of this Second Amendment,
and each such Loan Document shall hereafter be construed and interpreted after
giving full force and effect to the terms of this Second Amendment. As amended,
modified and supplemented pursuant to this 

                                      -2-

<PAGE>   8


Second Amendment, Borrower, Parent Company, ESBI and BCSI hereby ratify,
confirm and restate each Loan Document to which it is a party and agrees that
each such Loan Document shall continue in full force and effect. Each of the
Loan Documents now or hereafter executed and delivered pursuant to the terms
hereof or pursuant to the terms of the Credit Agreement, as amended hereby, or
as further evidence of or security for or in connection with the Credit
Agreement, as amended hereby, is hereby amended to the extent necessary so that
any reference in any such documents, instruments or agreements to the Credit
Agreement shall be a reference to the Credit Agreement as amended hereby.

         10. In the event that any one or more of the provisions contained in
this Second Amendment shall be determined invalid, illegal or unenforceable in
any respect for any reason, the validity, legality and enforceability of any
such provision or provisions in every other respect and the remaining
provisions of this Second Amendment shall not be impaired in any way.

         11. When required or implied by the context used, defined terms used
herein shall include the plural as well as the singular, and vice versa.

         12. This Second Amendment shall be governed by and construed in
accordance with the internal laws of the State of Texas and applicable federal
laws of the United States of America. This Second Amendment has been entered
into in Bexar County, Texas and shall be performable for all purposes in Bexar
County, Texas. The courts within the State of Texas shall have jurisdiction
over any and all disputes arising under or pertaining to this Second Amendment;
and any such dispute shall be heard in the county or judicial district of the
principal place of business of The Frost National Bank.

         13. This Second Amendment shall be binding upon and inure to the
benefit of all parties hereto and their respective successors and assigns;
provided, however, that neither Borrower nor Parent Company nor ESBI nor BCSI
nor any of their respective successors or assigns may, without the prior
written consent of all of the Banks, assign any rights, powers, duties or
obligations hereunder.

         14. This Second Amendment may be executed in any number of
counterparts and by different parties hereto on separate counterparts, each of
which when so executed shall be deemed to be an original and all of which when
taken together shall constitute but one and the same instrument.

         15. This Second Amendment constitutes a Loan Document.

         16. Upon execution of this Second Amendment by the Banks, Borrower,
Parent Company, ESBI and BCSI shall deliver to the Agent, in form and substance
satisfactory to the Agent, the certificates and documents described on Annex A.


                           [signatures on next page]


<PAGE>   9


         IN WITNESS WHEREOF, the parties hereto have caused this Second
Amendment to be duly executed by their respective authorized signatories as of
the day and year first above written.

                   BORROWER:

                   BILLING CONCEPTS, INC.


                   By:       /s/ Kelly E. Simmons
                      ---------------------------------------------------------
                   Name:     Kelly E. Simmons
                        -------------------------------------------------------
                   Title:   Executive Vice President & Chief Financial Officer
                         ------------------------------------------------------

                   PARENT COMPANY:

                   BILLING CONCEPTS CORP.


                   By:      /s/ Kelly E. Simmons
                      ---------------------------------------------------------
                   Name:    Kelly E. Simmons
                        -------------------------------------------------------
                   Title:   Executive Vice President & Chief Financial Officer
                         ------------------------------------------------------


                   GUARANTORS:

                   ENHANCED SERVICES BILLING, INC.


                   By:      /s/ Kelly E. Simmons
                      ---------------------------------------------------------
                   Name:    Kelly E. Simmons
                        -------------------------------------------------------
                   Title:   Executive Vice President & Chief Financial Officer
                         ------------------------------------------------------

                   BILLING CONCEPTS CORP.


                   By:       /s/ Kelly E. Simmons
                      ---------------------------------------------------------
                   Name:     Kelly E. Simmons
                        -------------------------------------------------------
                   Title:    Executive Vice President & Chief Financial Officer
                         ------------------------------------------------------

                   BILLING CONCEPTS SYSTEMS, INC.


                   By:       /s/ Kelly E. Simmons
                      ---------------------------------------------------------
                   Name:     Kelly E. Simmons
                        -------------------------------------------------------
                   Title:    Executive Vice President & Chief Financial Officer
                         ------------------------------------------------------


                    [signatures continued on following page]


<PAGE>   10


                   BANKS:

                   THE FROST NATIONAL BANK
                   Individually, as the Issuing Bank and as the Agent


                   By:      /s/ Gregg M. Chinn
                      ---------------------------------------------------------
                        Gregg M. Chinn, Vice President


                   NATIONSBANK, N.A., successor to
                   THE BOATMEN'S NATIONAL BANK OF ST. LOUIS


                   By:      /s/ Steven A. Linton
                      ---------------------------------------------------------
                        Steven A. Linton, Assistant Vice President