<PAGE>   1
                                                                    EXHIBIT 10.3

                                PARENT GUARANTY


              This Parent Guaranty (the "Guaranty") is made as of the 20th day
of December, 1996 by BILLING INFORMATION CONCEPTS CORP., a corporation
organized under the laws of the State of Delaware (the "Guarantor"), in favor
of THE FROST NATIONAL BANK, a national banking association ("Frost Bank") and
its successors and assigns, as agent (the "Agent") for the equal and ratable
benefit of the banks and other financial institutions listed on the signature
pages of and any other bank or financial institution that may hereafter become
a party to the hereinafter described Credit Agreement in accordance with the
terms thereof (hereinafter collectively referred to as the "Banks").

                             PRELIMINARY STATEMENT

              1.     Frost Bank, individually, as the Issuing Bank and the
Agent, and the other Banks have entered into a Credit Agreement dated as of
December 20, 1996 (as it may hereafter be amended or otherwise modified from
time to time, the "Credit Agreement") with BILLING INFORMATION CONCEPTS, INC.,
a Delaware corporation ("Borrower"), and Guarantor.  Borrower is a wholly owned
Subsidiary of Guarantor.  The Guarantor will derive substantial benefit,
whether directly or indirectly, from the making of the Loans and the issuing of
Letters of Credit by the Banks pursuant to the terms and conditions set forth
in the Credit Agreement.  It is a condition precedent to the effectiveness of
the Credit Agreement and the making of the Loans by the Banks under the Credit
Agreement that the Guarantor shall have executed and delivered this Guaranty.
Unless otherwise defined herein, the capitalized terms used herein which are
defined in the Credit Agreement shall have the meanings specified therein.

       NOW, THEREFORE, in consideration of the premises and other good and
valuable consideration, the adequacy, receipt and sufficiency of which are
hereby acknowledged, the Guarantor hereby agrees as follows:

       SECTION 1.  Guaranty.  Subject to Section 22 hereof, the Guarantor
hereby unconditionally and irrevocably (a) guarantees the punctual payment when
due (following any applicable grace period or opportunity to cure), whether at
stated maturity, by acceleration, by prepayment or otherwise, of all
obligations to the Agent and the Banks now or hereafter existing under the
Credit Agreement, the Notes and all other Loan Documents, whether for
principal, interest, prepayment premium, fees, expenses, taxes, costs, losses,
compensation, reimbursements or any other amount payable to the Agent and the
Banks under the terms of the Credit Agreement, the Notes and the other Loan
Documents, and (b) agrees to pay any and all expenses (including, without
limitation, reasonable counsel fees and expenses) incurred by the Agent and the
Banks in enforcing any rights under this Guaranty (all of the above being
hereinafter called the "Obligations").

       SECTION 2.  Guaranty Absolute.  The Guarantor guarantees that the
Obligations will be paid strictly in accordance with the terms of the Credit
Agreement, the Notes and all other Loan Documents (subject to any applicable
grace period or opportunity to cure), regardless of any law, regulation or
order now or hereafter in
<PAGE>   2
effect in any jurisdiction affecting any of such terms or the rights of the
Banks with respect thereto.  The liability of the Guarantor under this Guaranty
shall be absolute and unconditional irrespective of:

       (a)    any lack of validity or enforceability of or defect or deficiency
in the Credit Agreement, the Notes, the Letters of Credit or any of the other
Loan Documents;

       (b)    any change in the time, manner, terms or place of payment of, or
in any other term of, all or any of the Obligations, or any other amendment or
waiver of or any consent to departure from the Credit Agreement, the Notes, the
Letters of Credit or any of the other Loan Documents;

       (c)    any sale, exchange, release or non-perfection of any property
standing as security for the liabilities hereby guaranteed or any liabilities
incurred directly or indirectly hereunder or any set-off against any of said
liabilities, or any release or amendment or waiver of or consent to departure
from any other guaranty, for all or any of the Obligations;

       (d)    any change in the existence, structure or ownership of the
Guarantor or any other Company, or any insolvency, bankruptcy, reorganization
or other similar proceeding affecting such Company or such Company's assets;

       (e)    the existence of any claim, set-off or other rights which the
Guarantor may have at any time against any other Company, the holder or holders
of the Notes, the issuers of the Letters of Credit or any other Person, whether
or not arising in connection with this Guaranty, the Credit Agreement, the
Notes, the Letters of Credit or any other Loan Document; provided that nothing
contained herein shall prevent the assertion of any such claim by separate suit
or compulsory counterclaim;

       (f)    failure, omission, delay, neglect, refusal or lack of diligence
by any Bank or the Agent or any other Person to assert, enforce, give notice of
intent to exercise, or any other notice with respect to, or exercise any right,
privilege, power or remedy conferred on any Bank or the Agent or any other
Person in any of the Loan Documents or by law or action on the part of any Bank
or the Agent or any other Person granting indulgence, grace, adjustment,
forbearance or extension of any kind to Guarantor, any other Company or any
other Person;

       (g)    release, surrender, exchange, subordination or loss of any
security or lien priority under any of the Loan Documents or in connection with
the Obligations;

       (h)    release, modification or waiver of, or failure, omission, delay,
neglect, refusal or lack of diligence to enforce, any guaranty, pledge,
mortgage, deed of trust, security agreement, lien, charge, insurance agreement,
bond, letter of credit or other security device, guaranty, surety or indemnity
agreement whatsoever;

       (i)    failure by any Bank, the Agent or any other Person to notify, or
timely notify, the Guarantor of any default, event of default or similar event
(however denominated) under any of the Loan Documents, any renewal, extension,
supplementing, modification, rearrangement, amendment, restatement,
replacement, cancellation, rescission, revocation or reinstatement (whether or
not material) or assignment





                                      -2-
<PAGE>   3
of any part of the Obligations, release or exchange of any security, any other
action taken or not taken by any Bank or the Agent against the Guarantor, any
other Company or any other Person or any direct or indirect security for any
part of the Obligations, any new agreement between any Bank or the Agent and
any other Company or any other Person or any other event or circumstance.
Except as required by applicable law or as otherwise provided in the Loan
Documents, neither the Agent nor any Bank has any duty or obligation to give
the Guarantor (in its capacity as a guarantor hereunder) any notice of any kind
under any circumstances whatsoever with respect to or in connection with the
Obligations or the Loan Documents; or

       (j)    any other circumstance which might otherwise constitute a defense
available to, or a discharge of any other Company or any other Person
(including any guarantor) in respect of the Obligations, other than payment in
full of the Obligations.

This Guaranty shall continue to be effective or be reinstated, as the case may
be, if at any time any payment of any of the Obligations is annulled, set
aside, invalidated, declared to be fraudulent or preferential, rescinded or
must otherwise be returned, refunded or repaid by the Banks or the proceeds of
collateral are required to be returned by the Banks upon the insolvency,
bankruptcy, dissolution, liquidation or reorganization of any other Company, or
upon or as a result of the appointment of a receiver, intervenor or conservator
of, or trustee or similar officer for, any other Company or any substantial
part of such Company's respective property or otherwise, all as though such
payment or payments had not been made.  The obligations of the Guarantor under
this Guaranty shall not be subject to reduction, termination or other
impairment by reason of any setoff, recoupment, counterclaim or defense or for
any other reason.

       SECTION 3.  Continuing Guaranty.  This is a continuing Guaranty, and all
extensions of credit and financial accommodations heretofore, concurrently
herewith or hereafter made by the Banks and the Agent to Borrower and all
indebtedness of Borrower now owned or hereafter acquired by the Banks and the
Agent in connection with the transactions contemplated under the Credit
Agreement shall be conclusively presumed to have been made or acquired in
acceptance hereof.

       SECTION 4.  Waiver.  This is an absolute Guaranty of payment and not of
collection, and the Guarantor hereby waives (a) promptness, diligence, notice
of acceptance, presentment, demand, protest, notice of protest and dishonor,
notice of intent to accelerate, notice of acceleration and any other notice
with respect to any of the Obligations and this Guaranty; and (b) any
requirement that the Agent or any Bank protect, secure, perfect or insure any
security interest or Lien on any property subject thereto or exhaust any right
or take any action against any other Company or any other Person or any
Collateral or that any other Company or any other Person be joined in any
action hereunder.  Should the Agent or any Bank seek to enforce the obligations
of the Guarantor hereunder by action in any court, the Guarantor waives any
necessity, substantive or procedural, that a judgment previously be rendered
against Borrower or any other Person, or that any action be brought against any
other Company or any other Person, or that any other Company or any other
Person should be joined in such cause.  Such waiver shall be without prejudice
to the Agent or any Bank at their option to proceed against any other Company
or any other Person, whether by separate action or by joinder.





                                      -3-
<PAGE>   4
       SECTION 5.  Several Obligations. The obligations of the Guarantor
hereunder are several from any other Company or any other Person, and are
primary obligations concerning which the Guarantor is the principal obligor.
The Guarantor agrees that this Guaranty shall not be discharged except by
complete performance of the Obligations of Borrower under the Notes, the Credit
Agreement and the other Loan Documents and the obligations of the Guarantor
hereunder.  The obligations of the Guarantor hereunder shall not be affected in
any way by any receivership, insolvency, bankruptcy or other proceedings
affecting any other Company or any other Person or any of such Company's or
such Person's assets, or the release or discharge of any other Company or any
other Person from the performance of any obligation contained in any promissory
note or other instrument issued in connection with, evidencing or securing any
indebtedness guaranteed by this instrument, whether occurring by reason of law
or any other cause, whether similar or dissimilar to the foregoing.

       SECTION 6.  Subrogation.  The Guarantor will not exercise any rights
which it may acquire by way of subrogation under this Guaranty, by any payment
made hereunder or otherwise, until the termination of the obligations of the
Banks to make Loans and issue Letters of Credit under the Credit Agreement and
the indefeasible payment in full thereafter of all the Obligations.  If any
amount shall be paid to the Guarantor on account of such subrogation rights at
any time when the Banks are obligated to make Loans and issue Letters of Credit
under the Credit Agreement or when all the Obligations shall not have been
indefeasibly paid in full, such amount shall be held in trust for the benefit
of the Banks and shall forthwith be paid to the Agent to be applied to the
Obligations in such order as the Agent shall select.  If (a) the Guarantor
shall make payment to the Agent of all or any part of the Obligations and (b)
the obligations of the Banks to make Loans and issue Letters of Credit under
the Credit Agreement shall be terminated and all of the Obligations shall be
paid in full thereafter, the Agent will, at the Guarantor's request, execute
and deliver to the Guarantor appropriate documents, without recourse and
without representation or warranty, necessary to evidence the transfer by
subrogation to the Guarantor of any interest in the Obligations resulting from
such payment by the Guarantor.

       SECTION 7.  Subordination of Borrower's Obligations to the Guarantor.
The Guarantor agrees that if, for any reason whatsoever, Borrower now or
hereafter owes any indebtedness, directly or indirectly, to the Guarantor, or
the Guarantor now or hereafter owes any indebtedness, directly or indirectly,
to any other guarantor of the Obligations, all such indebtedness, together with
all interest thereon and fees and other charges in connection therewith, and
all Liens securing any such indebtedness shall at all times be second,
subordinate and inferior in right of payment, in lien priority and in all other
respects to the Obligations and the fulfillment of any of the Guarantor's
obligations hereunder or under any of the other Loan Documents.  The provisions
of this Section 7 are in addition to, and cumulative of, any other provisions
contained in any other Loan Document or other document, instrument or writing.

       SECTION 8.  Stay of Acceleration.  If acceleration of the time for
payment of any amount payable by Borrower under the Credit Agreement or the
Notes is stayed upon the insolvency, bankruptcy or reorganization of Borrower,
all such amounts otherwise subject to acceleration under the terms of the
Credit Agreement shall nonetheless be payable by the Guarantor hereunder
forthwith on demand by the holder or holders of the Notes.  The Guarantor's
Obligations under this Guaranty shall not be limited by





                                      -4-
<PAGE>   5
any valuation, estimation or disallowance made in connection with any
proceedings filed under the United States Bankruptcy Code.

       SECTION 9.  Representations and Warranties. The Guarantor hereby
represents and warrants as follows:

       (a)    This Guaranty is, and all other documents and instruments
executed in connection herewith when delivered will be, legal, valid and
binding obligations of the Guarantor, enforceable against the Guarantor in
accordance with their respective terms, except as such enforceability may be
(i) limited by the effect of any Debtor Laws and (ii) subject to the effect of
general principles of equity (regardless of whether such enforceability is
considered in a proceeding in equity or at law).

       (b)    Upon giving effect to (a) the execution of this Guaranty and (b)
the consummation of the transactions contemplated under this Guaranty, the
following are true and correct after diligent investigation:

              (i)    The fair saleable value of the assets of the Guarantor
       exceeds the amount that will be required to be paid on or in respect of
       the existing debts and other liabilities (including, without limitation,
       pending or overtly threatened litigation in amounts in excess of
       effective insurance coverage and all other contingent liabilities) of
       the Guarantor as they mature.

              (ii)   The assets of the Guarantor do not constitute unreasonably
       small capital for the Guarantor to carry out its business as now
       conducted and as proposed to be conducted including the capital needs of
       the Guarantor, taking into account the particular capital requirements
       of the business conducted by the Guarantor, and projected capital
       requirements and capital availability thereof.

              (iii)  The Guarantor does not intend to incur debts beyond its
       ability to pay such debts as they mature (taking into account the timing
       and amounts of cash to be received by the Guarantor, and of amounts to
       be payable on or in respect of debt of the Guarantor).

              (iv)   The fair saleable value of the assets of the Guarantor is
       greater than the total fair value of the liabilities, including
       contingent, subordinated, absolute, fixed, matured or unmatured, and
       liquidated or unliquidated liabilities, of the Guarantor.

       (c)    The Guarantor has determined that its liability and obligation
under this Guaranty may reasonably be expected to substantially benefit it
directly or indirectly, and its board of directors has made that determination.
Borrower and the Guarantor are mutually dependent on each other in the conduct
of their respective businesses and are, and do business together with the other
Companies as, an integrated business enterprise. The maintenance and
improvement of Borrower's financial condition is vital to sustaining the
Guarantor's business and the transactions contemplated in the Credit Agreement
produce distinct and identifiable financial and economic direct or indirect
benefits to the Guarantor.  Such identifiable benefits include the general
improvement of the Guarantor's financial and economic condition. The Guarantor
has had full and complete access to the Loan Documents and all other papers
executed by any other





                                      -5-
<PAGE>   6
Company or any other Person in connection with the Obligations, has reviewed
them and is fully aware of the meaning and effect of their contents. The
Guarantor is fully informed of all circumstances which bear upon the risks of
executing this Guaranty and which a diligent inquiry would reveal. It has
adequate means to obtain from each Company on a continuing basis information
concerning the financial condition of the Companies, and is not depending on
the Agent or any Bank to provide such information, now or in the future. It
agrees that neither the Agent nor any Bank shall have an obligation to advise
or notify it or to provide it with any such data or information.  The execution
and delivery of this Guaranty is not a condition precedent (and neither the
Agent nor any Bank has in any way implied that the execution of this Guaranty
is a condition precedent) to the Agent's or any Bank's making, extending or
modifying any loan or any other financial accommodation to or for the
Guarantor.

       (d)    No bankruptcy or insolvency proceedings are pending or
contemplated by or against the Guarantor.

       SECTION 10.  Amendments, Etc.  No amendment or waiver of any provision
of this Guaranty nor consent to any departure by the Guarantor therefrom shall
in any event be effective unless the same shall be in writing and signed by the
Banks and then such waiver or consent shall be effective only in the specific
instance and for the specific purpose for which given; provided, however, that
no amendment, waiver or consent shall, unless in writing and signed by all of
the Banks, limit the liability of the Guarantor hereunder.

       SECTION 11.  Notices, Etc.  All notices and other communications
provided for hereunder shall be in writing (including telegraphic, telex,
facsimile or cable communication) and mailed, telegraphed, telexed,
transmitted, cabled or delivered, if to the Guarantor, at the address for the
Guarantor set forth on the signature page hereof; if to the Agent or any Bank,
at the address for the Agent or such Bank (as the case may be) set forth in the
Credit Agreement, or, as to each party, at such other address as shall be
designated by such party in a written notice to the other party.  All such
notices and communications shall, when mailed, telegraphed, telexed,
transmitted or cabled be effective when deposited in the mail, delivered to the
telegraph company, confirmed by telex answerback, transmitted by telecopier or
delivered to the cable company, respectively.

       SECTION 12.  No Waiver; Remedies.  No failure on the part of the Agent
or any Bank to exercise, and no delay in exercising, any right hereunder shall
operate as a waiver thereof; nor shall any single or partial exercise of any
right hereunder preclude any other or further exercise thereof or the exercise
of any other right. The remedies herein provided are cumulative and not
exclusive of any remedies provided by law.

       SECTION 13.  Right of Set-off.  Upon the occurrence and during the
continuance of any Event of Default, the Banks are hereby authorized at any
time and from time to time, without notice to the Guarantor (any such notice
being expressly waived by the Guarantor) to the fullest extent permitted by
law, to set off and apply any and all deposits (general or special, time or
demand, provisional or final) at any time held and other indebtedness at any
time owing by any Bank to or for the credit or the account of the Guarantor
against any and all of the obligations of the Guarantor now or hereafter
existing under this Guaranty, irrespective of whether or not any Bank shall





                                      -6-
<PAGE>   7
have made any demand under this Guaranty and although such obligations may be
contingent and unmatured.  Each Bank agrees promptly to notify the Guarantor
after any such set-off and application made by such Bank; provided that the
failure to give such notice shall not affect the validity of such set-off and
application. The rights of the Banks under this Section 13 are in addition to
other rights and remedies (including, without limitation, other rights of set-
off) which the Banks may have.

       SECTION 14.  Costs, Expenses and Taxes. The Guarantor agrees to pay, and
cause to be paid, the costs and expenses of the Agent and the Banks that are
set forth in Section 10.3 of the Credit Agreement in the manner set forth in
Section 10.3 of the Credit Agreement.  The Guarantor agrees to pay interest on
any expenses or other sums due to the Agent and the Banks thereunder that are
not paid when due (following any applicable grace period or opportunity to
cure) at the Default Rate.  In addition, subject to Section 10.8 of the Credit
Agreement, the Guarantor shall pay any and all stamp and other taxes payable or
determined to be payable in connection with the execution and delivery of this
Guaranty and any of the documents or instruments evidencing the Obligations,
and agrees to save the Agent and the Banks harmless from and against any and
all liabilities with respect to or resulting from any delay in paying or
omission to pay such taxes.  The agreements of the Guarantor contained in this
Section 14 shall survive the payment of all other amounts owing hereunder or
under any of the other Obligations.

       SECTION 15.  Indemnity.  To the fullest extent permitted by law and
subject to Section 10.8 of the Credit Agreement, the Guarantor agrees to
indemnify the Agent and the Banks and their respective officers, directors
employees, agents, attorneys and other professionals and consultants, insurers
and stockholders, and each of them, in the manner set forth in Section 10.4 of
the Credit Agreement.

       SECTION 16.  Separability.  Should any clause, sentence, paragraph,
subsection or Section of this Guaranty be judicially declared to be invalid,
unenforceable or void, such decision will not have the effect of invalidating
or voiding the remainder of this Guaranty, and the parties hereto agree that
the part or parts of this Guaranty so held to be invalid, unenforceable or void
will be deemed to have been stricken herefrom and the remainder will have the
same force and effectiveness as if such part or parts had never been included
herein.

       SECTION 17.  Captions.  The captions in this Guaranty have been inserted
for convenience only and shall be given no substantive meaning or significance
whatever in construing the terms and provisions of this Guaranty.

       SECTION 18.  Continuing Guaranty; Transfer of the Notes.  This Guaranty
is a continuing guaranty and shall (a) remain in full force and effect until
the termination of the obligations of the Banks to make Loans and issue Letters
of Credit under the Credit Agreement and the indefeasible payment in full
thereafter of the Obligations and the expiration and termination of all Letters
of Credit; (b) be binding upon the Guarantor, its successors and assigns; and
(c) inure to the benefit of and be enforceable by the Agent and the Banks and
their respective successors, transferees and assigns. Without limiting the
generality of the foregoing clause (c), the Agent and the Banks may assign or
otherwise transfer the Notes to any other Person or entity in accordance with
the terms and provisions set forth in Section 10.7 of the Credit Agreement, and





                                      -7-
<PAGE>   8
such other Person or entity shall thereupon become vested with all the rights
and benefits in respect thereof granted to the Agent and the Banks herein or
otherwise.

       SECTION 19.  Limitation by Law.  All rights, remedies and powers
provided in this Guaranty may be exercised only to the extent that the exercise
thereof does not violate any applicable provision of law, and all the
provisions of this Guaranty are intended to be subject to all applicable
mandatory provisions of law which may be controlling and to be limited to the
extent necessary so that they will not render this Guaranty invalid,
unenforceable, in whole or in part, or not entitled to be recorded, registered
or filed under the provisions of any applicable law.

       SECTION 20.  Survival of Representations and Warranties.  All
representations and warranties contained in this Guaranty or made in writing by
or on behalf of the Guarantor in connection herewith, shall survive the
execution and delivery of this Guaranty. Any investigation by the Agent or any
Bank shall not diminish in any respect whatsoever its right to rely on such
representations and warranties.

       SECTION 21.  Governing Law; Submission to Jurisdiction. THIS GUARANTY
SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE INTERNAL LAWS OF THE
STATE OF TEXAS (WITHOUT REGARD TO ANY CONFLICTS OF LAW PRINCIPLES).  THE
PARTIES EXPRESSLY ACKNOWLEDGE THAT (I) THEY INTEND THAT THIS AGREEMENT AND EACH
NOTE SHALL BE GOVERNED BY THE PROVISIONS (INCLUDING, WITHOUT LIMITATION, THE
RIGHT OF THE PARTIES TO SELECT THE GOVERNING LAW) OF THE UNIFORM COMMERCIAL
CODE AND NOT BY COMMON LAW AND (II) THE STATE OF TEXAS BEARS A REASONABLE
RELATIONSHIP TO THIS TRANSACTION AND NO OTHER STATE HAS A MATERIALLY GREATER
INTEREST IN THIS TRANSACTION THAN THE STATE OF TEXAS.  THE GUARANTOR HEREBY
SUBMITS TO THE NONEXCLUSIVE JURISDICTION OF THE UNITED STATES DISTRICT COURT
FOR THE WESTERN DISTRICT OF TEXAS AND OF ANY TEXAS STATE COURT SITTING IN TEXAS
FOR PURPOSES OF ALL LEGAL PROCEEDINGS ARISING OUT OF OR RELATING TO THIS
GUARANTY OR THE TRANSACTIONS CONTEMPLATED HEREBY.

       SECTION 22.  Limitation on Guaranteed Amount.  Any other provision of
this Guaranty notwithstanding, the amount guaranteed by the Guarantor hereunder
shall be limited to the extent, if any, required so that its obligations under
this Guaranty shall not be subject to avoidance under Section 548 of the
Federal Bankruptcy Code or to being set aside or annulled under any applicable
state law relating to fraud on creditors.  In determining the limitations, if
any, on the amount of the Guarantor's obligations hereunder pursuant to the
preceding sentence, any rights of subrogation or contribution which the
Guarantor may have under this Guaranty or applicable law shall be taken into
account.



                           [signatures on next page]





                                      -8-
<PAGE>   9
       IN WITNESS WHEREOF, the Guarantor has caused this Guaranty to be duly
executed by its respective officer thereunto duly authorized, as of the date
first above written.



                                   BILLING INFORMATION CONCEPTS CORP.


                                   By:  /s/ KELLY E. SIMMONS        
                                       ----------------------------------
                                   Name: Kelly E. Simmons           
                                        --------------------------------
                                   Title: Senior Vice President and
                                         -------------------------------
                                          Chief Financial Officer
                                         -------------------------------

                                   9311 San Pedro,  Suite 100
                                   San Antonio, Texas  78216-4471

                                   Facsimile:                                   
                                             -----------------------------------
                                   Attention:                                   
                                             -----------------------------------





                                      -9-