<PAGE>

                                                                   EXHIBIT 10(a)

                               FOURTH AMENDMENT TO
                      AMENDED AND RESTATED CREDIT AGREEMENT

         THIS FOURTH AMENDMENT TO AMENDED AND RESTATED CREDIT AGREEMENT
("Amendment") is made and entered into this _____ day of March, 2003, but
effective as of March 1, 2003 (the "Amendment Date"), by and among XETA
Technologies, Inc., an Oklahoma corporation (the "Borrower"), Bank One,
Oklahoma, N.A., and U.S. Bank National Association, as Lenders under the Credit
Agreement referred to below (the "Lenders"), and Bank One, Oklahoma, N.A., as
Agent (in such capacity, the "Agent"), with reference to the following:

         A.       The Borrower, the Lenders and the Agent are parties to that
certain Amended and Restated Credit Agreement dated as of October 31, 2001, as
amended by that certain First Amendment to Amended and Restated Credit Agreement
dated effective as of June 1, 2002, as further amended by that certain Second
Amendment to Amended and Restated Credit Agreement dated effective as of
September 10, 2002 and as further amended by that certain Third Amendment to
Amended and Restated Credit Agreement dated effective as of December 1, 2002
(the "Credit Agreement").

         B.       The Borrower has requested that the Lenders and the Agent (i)
extend the availability of the Revolving Credit Facility and the maturity of the
Revolving Loans, and (ii) waive certain Defaults arising by virtue of the
Borrower's failure to comply with certain financial covenants set forth in the
Credit Agreement. The Lenders and the Agent have agreed to the foregoing
requests, subject to the terms and conditions set forth in this Amendment.

         NOW, THEREFORE, in consideration of the premises and the mutual
covenants and agreements herein contained, and for other good and valuable
consideration, the receipt and adequacy of which are hereby acknowledged, the
parties hereby amend the Credit Agreement, effective as of the Amendment Date,
as follows:

1.       DEFINITIONS. Capitalized terms used herein (including capitalized terms
used in the recitals above) but not otherwise defined have the respective
meanings assigned to them in the Credit Agreement.

2.       WAIVERS. Effective as of the Amendment Date, and subject to the
Borrower's satisfaction of the conditions precedent set forth in Section 4 of
this Amendment, the Lenders and the Agent agree to waive the Borrower's
non-compliance with Section 6.24.2 (Debt Service Coverage Ratio) and Section
6.24.3 (Leverage Ratio) of the Credit Agreement at January 31, 2003, and any
consequences of such non-compliance (other than as set forth in this Amendment).
The foregoing waivers do not extend to any other existing Default or Unmatured
Default (whether or not known to the Borrower, the Lenders or the Agent) or to
any Default or Unmatured Default that may arise or occur after the Amendment
Date. Nothing contained in this Amendment shall be construed as waiving any
other term or condition of the Credit Agreement or any of the other Loan
Documents or as obligating the Lenders or the Agent to waive any future
noncompliance or Default.

<PAGE>

3.       MODIFICATION OF FACILITIES. Effective as of the Amendment Date, and
subject to the Borrower's satisfaction of the conditions precedent set forth in
this Amendment:

         A.       Extension of Revolving Credit Facility. The availability of
the Revolving Credit Facility and the maturity of the Revolving Loans are hereby
extended from March 31, 2003 to May 1, 2003. Accordingly, the definition of the
term "Revolving Credit Facility Termination Date" appearing in Section 1.1 of
the Credit Agreement is hereby amended by replacing the reference to the date
"October 31, 2002" (as subsequently amended to "November 30, 2002" and "March
31, 2003") with the date "May 1, 2003."

         B.       No Obligation to Grant Further Extensions. The Borrower
acknowledges that, notwithstanding the references in the Credit Agreement and
this Amendment to dates or periods of time subsequent to May 1, 2003, (i) the
Lenders will not be obligated to further extend the availability of the
Revolving Credit Facility, (ii) the Lenders have given no assurances or
commitment that any extension request will be approved, (iii) the Lenders may
refuse any extension request in the exercise of their sole and absolute
discretion, and (iv) if any extension request is approved, the Lenders may
condition such approval on the Borrower's satisfaction of certain requirements,
including the making of further modifications to the Credit Agreement and/or the
terms of the Facilities.

         C.       Renewal Note. The Borrower agrees to make, execute and deliver
to each Lender a renewal Revolving Note (each, a "Renewal Revolving Note"),
substantially in the form attached hereto as Exhibit "F-1B." The Renewal
Revolving Notes are hereinafter collectively referred to as the "Renewal Notes."
The Renewal Notes shall be in renewal, extension and replacement of, but not in
satisfaction or as a novation of, the respective Notes delivered pursuant to the
Credit Agreement, and from and after the Amendment Date, unless the context
otherwise requires, all references to the "Revolving Notes" appearing in the
Credit Agreement or any other Loan Documents shall mean and refer to the Renewal
Revolving Notes.

         D.       Cross Collateralization and Cross Default of Notes.
Notwithstanding language to the contrary or consistent with the same, the
Borrower agrees and acknowledges that all assets pledged as collateral for any
one term or revolving credit facility hereby collateralizes all and any other
credit facility in favor of Lenders. Additionally, Borrower agrees and
acknowledges that any default on any one term or revolving credit facility is a
default on all and any other credit facility.

4.       CONDITIONS PRECEDENT. This Amendment shall become effective as of the
Amendment Date, subject to the Borrower's satisfaction of the following
conditions precedent (in addition to the conditions precedent set forth in
Article IV of the Credit Agreement):

         A.       Execution of Documents. The Borrower shall have duly and
validly authorized, executed and delivered to the Agent and the Lenders the
following documents, each in form and substance satisfactory to the Lenders:

                  (i)      this Amendment; and

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                  (ii)     the Renewal Revolving Notes;

         B.       Resolutions. The Agent shall have received a copy of the
resolutions of the Board of Directors of the Borrower authorizing the execution
and delivery of this Amendment and the performance by the Borrower of its
obligations under this Amendment, the Credit Agreement (as amended by this
Amendment) and the Renewal Notes.

         C.       Consent of Guarantor. The "Consent of Guarantor" appearing
after the Borrower's signature to this Amendment shall have been duly and
validly authorized, executed and delivered to the Lender by the Guarantor.

         D.       Accuracy of Representations and Warranties. All
representations and warranties made by the Borrower in the Credit Agreement and
the other Loan Documents shall be true and correct in all material respects as
of the Amendment Date (except to the extent any of such representations and
warranties with respect to the financial condition of the Borrower refer to an
earlier specified date).

         E.       No Default. There shall not have occurred any additional
Default or Unmatured Default as of the Amendment Date, and the Borrower shall be
current in payment of all principal, interest and fees due and owing to the
Agent or the Lenders as of the Amendment Date.

         F.       Waiver/Amendment Fee. The Borrower shall have paid to the
Agent, for the account of each Lender in accordance with each Lender' Pro Rata
Share, a waiver/amendment fee of $10,000.00.

5.       REPRESENTATIONS AND WARRANTIES. All representations and warranties of
Borrower contained in Article V of the Credit Agreement remain true and correct
(except to the extent any representations and warranties as to the Borrower's
financial condition relate solely to an earlier specified date) and are hereby
remade and restated as the date hereof and shall survive the execution and
delivery of this Amendment. The Borrower further represents and warrants as
follows:

         A.       Authority. The Borrower has all requisite power and authority
and has been duly authorized to execute, deliver and perform its obligations
under this Amendment, the Credit Agreement (as amended by this Amendment) and
the Renewal Notes.

         B.       Binding Obligations; Enforceability. This Amendment, the
Credit Agreement (as amended by this Amendment) and the Renewal Notes are valid
and legally binding obligations of the Borrower, enforceable in accordance with
their respective terms, except as limited by applicable bankruptcy, insolvency
or other laws affecting the enforcement of creditors' rights generally.

         C.       No Conflict; Government Consent. Neither the execution and
delivery by the Borrower of this Amendment and the Renewal Notes, nor the
consummation of the transactions therein contemplated, nor compliance with the
provisions thereof, will violate (i) any law, rule, regulation, order, writ,
judgment, injunction, decree or award binding on the Borrower or any of

                                       3

<PAGE>

its Subsidiaries, or (ii) the Borrower's or any Subsidiary's articles or
certificate of incorporation, partnership agreement, certificate of partnership,
articles or certificate of organization, by-laws, or operating or other
management agreement, as the case may be, or (iii) the provisions of any
indenture, instrument or agreement to which the Borrower or any of its
Subsidiaries is a party or is subject, or by which it, or its Property, is
bound, or conflict with or constitute a default thereunder, or result in, or
require, the creation or imposition of any Lien in, of or on the Property of the
Borrower or any of its Subsidiaries pursuant to the terms of any such indenture,
instrument or agreement. No order, consent, adjudication, approval, license,
authorization, or validation of, or filing, recording or registration with, or
exemption by, or other action in respect of any governmental or public body or
authority, or any subdivision thereof, which has not been obtained by the
Borrower or any of its Subsidiaries, is required to be obtained by the Borrower
or any of its Subsidiaries in connection with the execution and delivery of this
Amendment, the borrowings under the Credit Agreement (as amended hereby), the
payment and performance by the Borrower of the Obligations, or the legality,
validity, binding effect or enforceability of this Amendment, the Credit
Agreement (as amended by this Amendment) or the Renewal Notes.

         D.       No Material Adverse Change. Since January 31, 2003 (the date
of the latest financial statements of the Borrower which have been delivered to
the Agent and the Lenders), there has been no adverse change in the business,
Property, prospects, condition (financial or otherwise) or results of operations
of the Borrower and its Subsidiaries which could reasonably be expected to have
a Material Adverse Effect.

6.       MISCELLANEOUS.

         A.       Effect of Amendment. The terms of this Amendment shall be
incorporated into and form a part of the Credit Agreement. Except as amended,
modified and supplemented by this Amendment, the Credit Agreement shall continue
in full force and effect in accordance with its original stated terms, all of
which are hereby reaffirmed in every respect as of the date hereof. In the event
of any irreconcilable inconsistency between the terms of this Amendment and the
terms of the Credit Agreement, the terms of this Amendment shall control and
govern, and the agreements shall be interpreted so as to carry out and give full
effect to the intent of this Amendment. All references to the "Credit Agreement"
appearing in any of the Loan Documents shall hereafter be deemed references to
the Credit Agreement as amended, modified and supplemented by this Amendment.

         B.       Descriptive Headings. The descriptive headings of the several
sections of this Amendment are inserted for convenience only and shall not be
used in the construction of the content of this Amendment.

         C.       Governing Law. This Amendment shall be construed and enforced
in accordance with, and the rights of the parties shall be governed by, the laws
of the State of Oklahoma.

         D.       Reimbursement of Expenses. The Borrower agrees to pay the
reasonable fees and out-of-pocket expenses of The Drummond Law Firm, counsel to
the Agent, incurred in connection with the preparation of this Amendment in the
amount of $500.00 and the consummation of the transactions contemplated hereby.

                                       4

<PAGE>

         E.       Release by Borrower. In consideration of the waivers and other
agreements of the Lenders and the Agent contained herein, the Borrower, for
itself and its officers, directors, agents, employees, successors and assigns,
hereby releases, acquits and forever discharges each of the Lenders and the
Agent, and each of their respective parent, subsidiary and affiliated companies
and each of their respective officers, directors, agents, employees, successors,
and assigns, and all other persons acting for or on behalf of the Lenders and/or
the Agent, of and from any and all manner of actions, causes of actions, suits,
debts, accounts, conveyances, agreements, damages, claims, demands, liabilities,
costs, and expenses of whatsoever kind or nature, including attorney's fees, in
law or in equity, known or unknown, anticipated or unanticipated and howsoever
arising or accruing, which the Borrower may now have or may claim to have
against the parties released or any of them, including, without limitation,
those arising out of or relating in any way to the Credit Agreement or the
administration of the Facilities thereunder, any other Loan Document or any
other agreement or document relating to the Facilities. It is understood and
agreed by the Borrower that this is a full and final release covering any and
all of the Borrower's actions, claims, debts, judgment, damages, objections,
costs, attorney's fees, demands or liabilities, whether known or unknown,
undisclosed and/or unanticipated, which may have arisen, or may arise from any
act or omission, prior to the date of the execution and delivery of this
Amendment.

         F.       No Course of Dealing. This Amendment shall not establish a
course of dealing or be construed as evidence of any willingness or commitment
on the part of the Agent or the Lenders to grant other or future waivers or
consents, should any be requested, or to agree to other or future amendments to
or modifications of the Credit Agreement or the terms and conditions applicable
to the Facilities.

                [REMAINDER OF THIS PAGE INTENTIONALLY LEFT BLANK.
                      SIGNATURES APPEAR ON FOLLOWING PAGE.]

                                       5

<PAGE>

         IN WITNESS WHEREOF, the Borrower, the Lenders and the Agent have
executed and delivered this Amendment on the day and year first set forth above.

                                          XETA TECHNOLOGIES, INC.

                                          By: __________________________________
                                          Name:  Robert B. Wagner
                                          Title: Secretary and Chief Financial
                                                 Officer

Revolving Loan Commitment                 BANK ONE, OKLAHOMA, N.A.,
from and after Amendment Date:            Individually and as Agent
$1,100,000.00

                                          By: __________________________________
                                          Name:  Brett Hatchett
                                          Title: Vice President

Revolving Loan Commitment                 U.S. BANK NATIONAL ASSOCIATION
from and after Amendment Date:            (formerly known as Firstar Bank, N.A.,
$900,000.00                               successor by merger to Firstar Bank
                                          Missouri, National Association)

                                          By: __________________________________
                                          Name:  David L. Orf
                                          Title: Vice President

                                    EXHIBITS

Exhibit F-1B -        Form of Renewal Revolving Note

                                       6

<PAGE>

                              CONSENT OF GUARANTOR

         The undersigned hereby (i) acknowledges and consents to the execution
and delivery of the above and foregoing Third Amendment to Credit Agreement,
(ii) confirms that the Subsidiary Guaranty of the undersigned will continue in
full force and effect as security for payment and performance of all of the
"Guaranteed Obligations," as such term is used in the Subsidiary Guaranty, and
(iii) ratifies and reaffirms the Subsidiary Guaranty.

         No inference shall be drawn from the undersigned's execution of this
Consent that consent or approval of the undersigned is required for this or any
future modification or amendment of or supplement to the Credit Agreement or
other Loan Document, or for this or any future increase, decrease, extension or
renewal of the Guaranteed Obligations.

         Capitalized terms used in this Consent and not otherwise defined have
the respective meanings assigned to them in the Credit Agreement referred to in
the above and foregoing Second Amendment to Credit Agreement.

                                                 U.S. TECHNOLOGIES SYSTEMS, INC.

                                                 By: ___________________________
                                                 Name: _________________________
                                                 Title: ________________________

<PAGE>

                             RENEWAL REVOLVING NOTE
                                 (Exhibit F-1B)

$900,000                                                          March 1, 2003
                                                                 Tulsa, Oklahoma

         XETA Technologies, Inc., an Oklahoma corporation (the "Borrower"),
promises to pay to the order of U.S. BANK NATIONAL ASSOCIATION (the "Lender"),
the aggregate unpaid principal amount of all Revolving Loans made by the Lender
to the Borrower pursuant to Section 2.1.1 of the Agreement (as hereinafter
defined), in immediately available funds at the main office of Bank One,
Oklahoma, N.A., Tulsa, Oklahoma, as Agent, together with interest on the unpaid
principal amount hereof at the rates and on the dates set forth in the
Agreement. The Borrower shall pay the principal of and accrued and unpaid
interest on the Revolving Loans in full on the Revolving Credit Facility
Termination Date and shall make such mandatory payments as are required to be
made under the terms of Article II of the Agreement.

         The Lender shall, and is hereby authorized to, record on the schedule
attached hereto, or to otherwise record in accordance with its usual practice,
the date and amount of each Revolving Loan and the date and amount of each
principal payment hereunder.

         This Note is one of the Revolving Notes issued pursuant to, and is
entitled to the benefits of, the Amended and Restated Credit Agreement dated as
of October 31, 2001, as amended by that certain First Amendment to Amended and
Restated Credit Agreement dated effective as of June 1, 2002, as further amended
by that certain Second Amendment to Amended and Restated Credit Agreement dated
effective as of September 10, 2002, as further amended by that certain Third
Amendment to Amended and Restated Credit Agreement dated effective as of
December 1, 2002 and as further amended by that certain Fourth Amendment to
Amended and Restated Credit Agreement dated effective as of March 1, 2003
(which, as it may be further amended or modified and in effect from time to
time, is herein called the "Agreement"), among the Borrower, the lenders party
thereto, including the Lender, and Bank One, Oklahoma, N.A., as Agent.
Capitalized terms used herein and not otherwise defined herein are used with the
meanings attributed to them in the Agreement. Reference is made to the Agreement
for a statement of the terms and conditions governing this Note, including the
terms and conditions under which this Note may be prepaid or its maturity date
accelerated.

         This Note is secured pursuant to the Collateral Documents, as more
specifically described in the Agreement, and reference is made thereto for a
statement of the terms and provisions thereof. All assets of Borrower are
cross-pledged to all other facilities of the Lender and default on one facility
is a default on all or any other facility.

         This Note is made, executed and delivered by the Borrower and delivered
to the Lender in renewal, extension and decrease of and replacement for that
certain Revolving Note dated as of October 31, 2001, executed by the Borrower
payable to the order of the Lender in the stated principal amount of $2,250,000
(the "Prior Note"). All liens and security interests in Property securing
payment of the Prior Note shall continue in full force and effect, uninterrupted
and unabated, as security for payment of this Note.

                                XETA TECHNOLOGIES, INC., an Oklahoma corporation

                                By: ____________________________________________
                                    Print Name: Robert B. Wagner
                                    Title: Secretary and Chief Financial Officer

<PAGE>

                   SCHEDULE OF LOANS AND PAYMENTS OF PRINCIPAL
                                       TO
                RENEWAL REVOLVING NOTE OF XETA TECHNOLOGIES, INC.
                               DATED MARCH 1, 2003

<TABLE>
<CAPTION>
                     Principal                 Maturity            Principal
                     Amount of                of Interest            Amount            Unpaid
     Date              Loan                     Period                Paid             Balance
----------------------------------------------------------------------------------------------
<S>                  <C>                      <C>                  <C>                 <C>
March 1, 2003
</TABLE>

<PAGE>

                             RENEWAL REVOLVING NOTE

$1,100,000.00                                                     March 1, 2003
                                                                 Tulsa, Oklahoma

         XETA Technologies, Inc., an Oklahoma corporation (the "Borrower"),
promises to pay to the order of BANK ONE, OKLAHOMA, N.A. (the "Lender"), the
aggregate unpaid principal amount of all Revolving Loans made by the Lender to
the Borrower pursuant to Section 2.1.1 of the Agreement (as hereinafter
defined), in immediately available funds at the main office of Bank One,
Oklahoma, N.A., Tulsa, Oklahoma, as Agent, together with interest on the unpaid
principal amount hereof at the rates and on the dates set forth in the
Agreement. The Borrower shall pay the principal of and accrued and unpaid
interest on the Revolving Loans in full on the Revolving Credit Facility
Termination Date and shall make such mandatory payments as are required to be
made under the terms of Article II of the Agreement.

         The Lender shall, and is hereby authorized to, record on the schedule
attached hereto, or to otherwise record in accordance with its usual practice,
the date and amount of each Revolving Loan and the date and amount of each
principal payment hereunder.

         This Note is one of the Revolving Notes issued pursuant to, and is
entitled to the benefits of, the Amended and Restated Credit Agreement dated as
of October 31, 2001, as amended by that certain First Amendment to Amended and
Restated Credit Agreement dated effective as of June 1, 2002, as further amended
by that certain Second Amendment to Amended and Restated Credit Agreement dated
effective as of September 10, 2002, as further amended by that certain Third
Amendment to Amended and Restated Credit Agreement dated effective as of
December 1, 2002 and as further amended by that certain Fourth Amendment to
Amended and Restated Credit Agreement dated effective as of March 1, 2003
(which, as it may be further amended or modified and in effect from time to
time, is herein called the "Agreement"), among the Borrower, the lenders party
thereto, including the Lender, and Bank One, Oklahoma, N.A., as Agent.
Capitalized terms used herein and not otherwise defined herein are used with the
meanings attributed to them in the Agreement. Reference is made to the Agreement
for a statement of the terms and conditions governing this Note, including the
terms and conditions under which this Note may be prepaid or its maturity date
accelerated.

         This Note is secured pursuant to the Collateral Documents, as more
specifically described in the Agreement, and reference is made thereto for a
statement of the terms and provisions thereof. All assets of Borrower are
cross-pledged to all other facilities of the Lender and default on one facility
is a default on all or any other facility.

         This Note is made, executed and delivered by the Borrower and delivered
to the Lender in renewal, extension and decrease of and replacement for that
certain Revolving Note dated as of October 31, 2001, executed by the Borrower
payable to the order of the Lender in the stated principal amount of
$2,750,000.00 (the "Prior Note"). All liens and security interests in Property
securing payment of the Prior Note shall continue in full force and effect,
uninterrupted and unabated, as security for payment of this Note.

                                XETA TECHNOLOGIES, INC., an Oklahoma corporation

                                By: ____________________________________________
                                    Print Name: Robert B. Wagner
                                    Title: Secretary and Chief Financial Officer

<PAGE>

                   SCHEDULE OF LOANS AND PAYMENTS OF PRINCIPAL
                                       TO
                RENEWAL REVOLVING NOTE OF XETA TECHNOLOGIES, INC.
                               DATED MARCH 1, 2003

<TABLE>
<CAPTION>
                    Principal                 Maturity                    Principal
                    Amount of                of Interest                   Amount               Unpaid
     Date             Loan                     Period                       Paid                Balance
-------------------------------------------------------------------------------------------------------
<S>                 <C>                      <C>                          <C>                   <C>
March 1, 2003
</TABLE>