<PAGE>
                                                                   EXHIBIT 10.20

                       FIRST AMENDMENT TO CREDIT AGREEMENT
                                   AND WAIVER

         THIS FIRST AMENDMENT TO CREDIT AGREEMENT AND WAIVER, dated as of
October 31, 2003 (this "First Amendment"), is entered into by and among WEST
CORPORATION, a Delaware corporation (the "Borrower"), certain Domestic
Subsidiaries of the Borrower as Guarantors (the "Guarantors" and together with
the Borrower, the "Credit Parties"), the Required Lenders identified on the
signature pages hereto and WACHOVIA BANK, NATIONAL ASSOCIATION, as
administrative agent for the Lenders (the "Administrative Agent").

                               W I T N E S S E T H

         WHEREAS, the Borrower, the Guarantors, the Administrative Agent and the
Lenders are parties to that certain Credit Agreement dated as of May 9, 2003 (as
amended, modified, supplemented or restated from time to time, the "Credit
Agreement"; capitalized terms used herein shall have the meanings ascribed
thereto in the Credit Agreement unless otherwise defined herein);

         WHEREAS, the Borrower has notified the Lenders that it intends to
acquire Scherer Communications, Inc., a Texas corporation doing business as
ConferenceCall.com ("ConferenceCall.com"), pursuant to a Stock Purchase
Agreement, dated as of October 21, 2003, among the Borrower, as the buyer,
ConferenceCall.com, the stockholders of ConferenceCall.com, as the sellers, and
the other parties thereto (the "ConferenceCall.com Acquisition");

         WHEREAS, the Borrower has requested that the Required Lenders agree to
amend the definition of "Permitted Acquisition" in Section 1.1 of the Credit
Agreement;

         WHEREAS, the Borrower has requested that the Required Lenders waive
certain requirements set forth in the definition of "Permitted Acquisition" in
Section 1.1 of the Credit Agreement on a one-time basis in order to permit the
consummation of the ConferenceCall.com Acquisition; and

         WHEREAS, the Required Lenders have agreed to the amendment and waivers
requested by the Borrower, subject to the terms and conditions set forth herein.

         NOW, THEREFORE, IN CONSIDERATION of the premises and other good and
valuable consideration, the receipt and sufficiency of which is hereby
acknowledged, the parties hereto agree as follows:

                                       1
<PAGE>
                                    SECTION 1

                                    AMENDMENT

         1.1      DEFINITION OF PERMITTED ACQUISITION. The definition of
"Permitted Acquisition," as set forth in Section 1.1 of the Credit Agreement, is
hereby amended by deleting the figure "$20,000,000," appearing in clause (f) of
such definition, and inserting the figure "$50,000,000" in substitution
therefor. The definition of "Permitted Acquisition," as amended hereby, shall
read in its entirety as set forth below:

                  "Permitted Acquisition" shall mean an acquisition or any
         series of related acquisitions by a Credit Party of the assets or all
         of the Capital Stock of a Person or any division, line of business or
         other business unit of a Person (such Person or such division, line of
         business or other business unit of such Person referred to herein as
         the "Target"), in each case that is in the same line of business (or
         assets used in the same line of business) as the Credit Parties and
         their Subsidiaries or whereby a substantial portion of the acquired
         business relies upon automated transactions, telephone representatives
         or telephony technology, so long as (a) no Default or Event of Default
         shall then exist or would exist after giving effect thereto; (b) the
         Credit Parties shall demonstrate to the reasonable satisfaction of the
         Administrative Agent that the Credit Parties will be in compliance on a
         pro forma basis with all of the terms and provisions of the financial
         covenants set forth in Section 5.9; (c) the Administrative Agent, on
         behalf of the Lenders, shall have received (or shall receive in
         connection with the closing of such acquisition) a first priority
         perfected security interest in all of the Capital Stock acquired with
         respect to the Target and the Target, if a Person, shall have executed
         a Joinder Agreement in accordance with the terms of Section 5.10; (d)
         such acquisition is not a "hostile" public company acquisition and has
         been approved by the Board of Directors and/or shareholders of the
         applicable Credit Party and the public company Target; (e) after giving
         effect to such acquisition, the sum of (1) the unused availability
         under the Aggregate Revolving Committed Amount plus (2) the Cash and
         Cash Equivalents held by the Credit Parties is greater than or equal to
         $25,000,000; and (f) with respect to any acquisition where the total
         consideration shall be greater than $50,000,000, the Borrower shall
         have delivered to the Administrative Agent and each of the Lenders not
         less than twenty (20) Business Days prior to the consummation of such
         acquisition (i) a reasonably detailed description of the material terms
         of such acquisition (including, without limitation, the purchase price
         and method and structure of payment) and of each Target, (ii) audited
         financial statements of the Target for its two (2) most recent fiscal
         years prepared by independent certified public accountants acceptable
         to the Administrative Agent and unaudited fiscal year-to-date
         statements for the most recent interim periods, (iii) consolidated
         projected income statements of the Borrower and its Consolidated
         Subsidiaries (giving effect to such Permitted Acquisition and the
         consolidation with the Borrower of each relevant Target) for the three
         (3) year period following the consummation of such Permitted
         Acquisition, in reasonable detail, together with any appropriate
         statement of assumptions, and (iv) a certificate, in form and substance
         reasonably satisfactory to the Administrative Agent, executed by a
         Responsible Officer of

                                       2
<PAGE>
         the Borrower (A) certifying that such Permitted Acquisition complies
         with the requirements of this Credit Agreement and (B) demonstrating
         compliance with subsections (b) and (e) of this definition; provided,
         however, that an acquisition of a Target that is not incorporated,
         formed or organized in the United States (a "Foreign Target") shall
         only qualify as a Permitted Acquisition if each of the other
         requirements set forth in this definition shall have been satisfied and
         the total consideration for all such Foreign Targets does not exceed
         $50,000,000 in the aggregate during the term of this Credit Agreement.

                                    SECTION 2

WAIVER

         2.1      Waiver. The Required Lenders hereby waive, on a one-time basis
for the ConferenceCall.com Acquisition, the failure of the Borrower to comply
with Section 6.5 of the Credit Agreement, and more specifically, the
requirements set forth in the definition of "Permitted Acquisition," which
require the Borrower to provide the Lenders with (a) twenty Business Days'
notice prior to the consummation of any acquisition with total consideration in
excess of $20,000,000 and (b) audited financial statements of ConferenceCall.com
for its two most recent fiscal years. The Required Lenders consent to the
Borrower consummating the ConferenceCall.com Acquisition, on terms and
conditions substantially the same as those set forth on the summary of material
terms attached hereto as Schedule A. Except for the specific, one-time waiver
set forth above, nothing set forth herein or contemplated hereby is intended to
constitute a waiver of (i) any rights or remedies available to the Lenders or
the Administrative Agent under the Credit Agreement or any other Credit Document
or under applicable law (all of which rights and remedies are hereby expressly
reserved by the Lenders and the Administrative Agent) or (ii) the Credit
Parties' obligation to comply fully with any duty, term, condition, obligation
or covenant contained in the Credit Agreement and the other Credit Documents.

SECTION 3

CLOSING CONDITIONS AND POST-CLOSING REQUIREMENTS

         3.1      Closing Conditions.

         This First Amendment shall be effective as of the date hereof upon
satisfaction of the following conditions precedent, in form and substance
reasonably acceptable to the Administrative Agent:

                  (a) First Amendment. The Administrative Agent shall have
         received a copy of this First Amendment duly executed by each of the
         Credit Parties and the Required Lenders.

                                       3
<PAGE>
                  (b) Officer's Certificate. The Administrative Agent shall have
         received from the Credit Parties an officer's certificate executed by a
         Responsible Officer of the Borrower (i) certifying that the
         ConferenceCall.com Acquisition complies with the requirements of the
         Credit Agreement (subject to the waiver set forth herein) and (ii)
         demonstrating that, after giving effect to the ConferenceCall.com
         Acquisition, (A) the Credit Parties will be in compliance on a pro
         forma basis with the financial covenants set forth in Section 5.9 of
         the Credit Agreement and (B) the sum of (1) the unused availability
         under the Aggregate Revolving Committed Amount plus (2) the Cash and
         Cash Equivalents held by the Credit Parties shall be greater than or
         equal to $25,000,000.

                  (c) Financial Statements. The Lenders shall have received
         consolidated projected income statements of the Borrower and its
         Consolidated Subsidiaries (giving effect to the ConferenceCall.com
         Acquisition and the consolidation with the Borrower of
         ConferenceCall.com) for the three (3) year period following the
         consummation of the acquisition, in reasonable detail, together with
         any appropriate statement of assumptions.

         3.2      Post-Closing Requirements.

                  (a) Pledge of Stock. As soon as possible, and in any event no
         later than three (3) Business Days after the closing date of the
         ConferenceCall.com Acquisition (or such later date as agreed to by the
         Administrative Agent in its sole discretion), the Administrative Agent,
         on behalf of the Lenders, shall have received a first priority
         perfected security interest in all Capital Stock acquired by the Credit
         Parties with respect to the ConferenceCall.com Acquisition.

                  (b) Joinder Agreement. As soon as possible, and in any event
         no later than three (3) Business Days after the closing date of the
         ConferenceCall.com Acquisition (or such later date as agreed to by the
         Administrative Agent in its sole discretion), the Administrative Agent
         shall have received a Joinder Agreement duly executed by
         ConferenceCall.com and the Borrower, in accordance with the terms of
         Section 5.10 of the Credit Agreement.

                  (c) Authority Documents. As soon as possible, and in any event
         no later than three (3) Business Days after the closing date of the
         ConferenceCall.com Acquisition (or such later date as agreed to by the
         Administrative Agent in its sole discretion), the Administrative Agent
         shall have received a certificate signed by the secretary of
         ConferenceCall.com attaching the following authority documents of
         ConferenceCall.com and certifying that the same are true and complete
         as of the closing date of the ConferenceCall.com Acquisition: (i) a
         copy of its articles of incorporation, (ii) a copy of the resolutions
         of its board of directors, approving and adopting the Joinder Agreement
         and the other Credit Documents, (iii) a copy of its bylaws, (iv) copies
         of a certificate of good standing, existence or its equivalent
         certified as of a recent date by the appropriate Governmental Authority
         of its state of incorporation and (v) an incumbency certificate.

                                       4
<PAGE>
                  (d) Legal Opinion. As soon as possible, and in any event no
         later than thirty (30) Business Days after the closing date of the
         ConferenceCall.com Acquisition (or such later date as agreed to by the
         Administrative Agent in its sole discretion), the Administrative Agent
         shall have received a legal opinion from counsel to the Credit Parties
         relating to ConferenceCall.com, in the same form and substance as the
         opinions given with respect to the original Guarantors and in form and
         substance reasonably satisfactory to the Administrative Agent.

                  (e) Effect of Non-Compliance. Notwithstanding the terms of
         Section 7.1(c) of the Credit Agreement to the contrary, the failure of
         any requirement set forth in this Section 3.2 to be satisfied within
         the time period allotted therefor shall constitute an immediate Event
         of Default under the Credit Agreement.

SECTION 4

MISCELLANEOUS

         4.1      Amended Terms. The term "Credit Agreement" as used in each of
the Credit Documents shall hereafter mean the Credit Agreement as amended by
this First Amendment. Except as specifically amended or modified hereby or
otherwise agreed, the Credit Agreement is hereby ratified and confirmed and
shall remain in full force and effect according to its terms.

         4.2      Representations and Warranties of the Borrower. Each of the
Credit Parties represents and warrants to the Lenders as follows:

                  (a) It has taken all necessary action to authorize the
         execution, delivery and performance of this First Amendment.

                  (b) This First Amendment has been duly executed and delivered
         by such Person and constitutes such Person's legal, valid and binding
         obligations, enforceable in accordance with its terms, except as such
         enforceability may be subject to (i) bankruptcy, insolvency,
         reorganization, fraudulent conveyance or transfer, moratorium or
         similar laws affecting creditors' rights generally and (ii) general
         principles of equity (regardless of whether such enforceability is
         considered in a proceeding at law or in equity).

                  (c) No consent, approval, authorization or order of, or
         filing, registration or qualification with, any court or Governmental
         Authority or third party is required in connection with the execution,
         delivery or performance by such Person of this First Amendment.

                  (d) The representations and warranties of such Person set
         forth in Article III of the Credit Agreement are, subject to the
         limitations set forth therein, true and correct in all material
         respects as of the date hereof (except for those which expressly relate
         to an earlier date); provided that Schedule 3.12 to the Credit
         Agreement shall be revised to reflect certain

                                       5
<PAGE>
         changes occurring since the original Closing Date within three (3)
         Business Days after the closing date of the ConferenceCall.com
         Acquisition.

         4.3      Reaffirmation of Credit Party Obligations. Each Credit Party
hereby ratifies the Credit Agreement (as amended by this First Amendment) and
acknowledges and reaffirms (a) that it is bound by all terms of the Credit
Agreement (as amended by this First Amendment) applicable to it and (b) that it
is responsible for the observance and full performance of its respective Credit
Party Obligations.

         4.4      Credit Document. This First Amendment shall constitute a
Credit Document under the terms of the Credit Agreement.

         4.5      Expenses. The Borrower agrees to pay all reasonable costs and
expenses of the Administrative Agent in connection with the preparation,
execution and delivery of this First Amendment, including, without limitation,
the reasonable fees and expenses of Moore & Van Allen, PLLC, and all previously
incurred fees and expenses which remain outstanding on the date hereof.

         4.6      Entirety. This First Amendment and the other Credit Documents
embody the entire agreement between the parties hereto and supersede all prior
agreements and understandings, oral or written, if any, relating to the subject
matter hereof.

         4.7      Counterparts/Telecopy. This First Amendment may be executed in
any number of counterparts, each of which when so executed and delivered shall
be an original, but all of which shall constitute one and the same instrument.
Delivery of executed counterparts of the First Amendment by telecopy shall be
effective as an original and shall constitute a representation that an original
shall be delivered.

         4.8      Governing Law. This First Amendment and the rights and
obligations of the parties under this First Amendment shall be governed by, and
construed and interpreted in accordance with, the law of the State of New York.

         4.9      Consent to Jurisdiction; Service of Process; Waiver of Jury
Trial. The jurisdiction, services of process and waiver of jury trial provisions
set forth in Sections 9.14 and 9.17 of the Credit Agreement are hereby
incorporated by reference, mutatis mutandis.

         4.10     Further Assurances. The Credit Parties agree to promptly take
such action, upon the request of the Administrative Agent, as is reasonably
necessary to carry out the intent of this First Amendment.

                            [Signature Pages Follow]

                                       6
<PAGE>

         IN WITNESS WHEREOF, each of the parties hereto has caused a counterpart
of this First Amendment to be duly executed under seal and delivered as of the
date and year first above written.

BORROWER:                            WEST CORPORATION,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

GUARANTORS:                          WEST TELEMARKETING CORPORATION,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     WEST TELEMARKETING CORPORATION II,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     WEST TELEMARKETING CORPORATION
                                     OUTBOUND, a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     DAKOTAH DIRECT II, L.L.C.,
                                     a Delaware limited liability company

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Manager

                                     WEST INTERACTIVE CORPORATION,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

GUARANTORS CONT.:                    WEST FACILITIES CORPORATION,


                                        7
<PAGE>
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     WEST DIRECT, INC.,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     NORTHERN CONTACT, INC.,
                                     a Delaware limited liability company

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     TEL MARK SALES, INC.,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     INTERCALL HOLDING CORPORATION,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     INTERCALL, INC.,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                       8
<PAGE>
GUARANTORS CONT.:                    ITC SERVICE COMPANY,
                                     a Georgia corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     ITC TELECOM VENTURES, INC.,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     ITC WIRELESS, INC.,
                                     a Delaware corporation

                                     By: /s Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     INVIEW, INC.,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     INTERCALL WEB CONFERENCING, INC.,
                                     a Delaware corporation

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Chief Financial Officer/Treasurer

                                     ATTENTION, LLC,
                                     a Delaware limited liability company

                                     By: /s/ Paul M. Mendlik
                                        ----------------------------------------
                                     Name: Paul M. Mendlik
                                     Title: Manager

                                       9
<PAGE>

AGENT AND LENDERS:                   WACHOVIA BANK, NATIONAL ASSOCIATION,
                                     as Administrative Agent, Issuing Lender,
                                     Swingline Lender and as a Lender

                                     By: /s/ Michael Romanzo
                                        ----------------------------------------
                                     Name: Michael Romanzo
                                     Title: Vice President

                           [signature pages continue]

                                       10
<PAGE>

                                     WELLS FARGO BANK NATIONAL ASSOCIATION

                                     By: /s/ Daniel A. Toll
                                        ----------------------------------------
                                     Name: Daniel A. Toll
                                     Title: Vice President

                           [signature pages continue]

                                       11
<PAGE>

                                     BANK OF AMERICA, N.A.

                                     By: /s/ Steven K. Kessler
                                        ----------------------------------------
                                     Name: Steven K. Kessler
                                     Title: Senior Vice President

                           [signature pages continue]

                                       12
<PAGE>

                                     BNP PARIBAS

                                     By: /s/ Peter C. Labrie
                                        ----------------------------------------
                                     Name: Peter C. Labrie
                                     Title: Central Region Manager

                                     By: /s/ Barbara V. Rivera
                                        ----------------------------------------
                                     Name: Barbara V. Rivera
                                     Title: Vice President

                           [signature pages continue]

                                       13
<PAGE>

                                     U.S. BANK, N.A.

                                     By: /s/ Karen Nelson
                                        ----------------------------------------
                                     Name: Karen Nelson
                                     Title: Vice President

                           [signature pages continue]

                                       14
<PAGE>

                                     LASALLE BANK NATIONAL ASSOCIATION

                                     By: /s/ Lezlee Schutty
                                        ----------------------------------------
                                     Name: Lezlee Schutty
                                     Title: Commercial Banking Officer

                           [signature pages continue]

                                       15
<PAGE>

                                     THE BANK OF NOVA SCOTIA

                                     By: /s/ M. Kus
                                        ----------------------------------------
                                     Name: M. Kus
                                     Title: Director

                           [signature pages continue]

                                       16
<PAGE>

                                     FIRST NATIONAL BANK OF OMAHA

                                     By: /s/ Mark A. Baratta
                                        ----------------------------------------
                                     Name: Mark A. Baratta
                                     Title: Vice President

                           [signature pages continue]

                                       17
<PAGE>

                                     KEY BANK NATIONAL ASSOCIATION

                                     By: /s/ Vijaya Kulkarni
                                        ----------------------------------------
                                     Name: Vijaya Kulkarni
                                     Title: AVP

                           [signature pages continue]

                                       18
<PAGE>

                                     UNION BANK OF CALIFORNIA, N.A.

                                     By: /s/ Mehmet Mumcuoglu
                                        ----------------------------------------
                                     Name: Mehmet Mumcuoglu
                                     Title: Vice President

                           [signature pages continue]

                                       19
<PAGE>

                                     COMERICA BANK

                                     By: /s/ Timothy O'Rourke
                                        ----------------------------------------
                                     Name: Timothy O'Rourke
                                     Title: Vice President

                           [signature pages continue]

                                       20
<PAGE>

                                     THE NORTHERN TRUST COMPANY

                                     By: /s/ Mark E. Taylor
                                        ----------------------------------------
                                     Name: Mark E. Taylor
                                     Title: Vice President

                           [signature pages continue]

                                       21
<PAGE>

                                     COMMERCIAL FEDERAL BANK

                                     By: /s/ William Honke
                                        ----------------------------------------
                                     Name: William Honke
                                     Title: Vice President

                           [signature pages continue]

                                       22
<PAGE>

                                     RZB FINANCE LLC, CONNECTICUT OFFICE


                                     By: /s/ Astrid Wilke
                                        ----------------------------------------
                                     Name: Astrid Wilke
                                     Title: Vice President

                                     By: /s/ Christoph Hoedl
                                        ----------------------------------------
                                     Name: Christoph Hoedl
                                     Title: Vice President

                           [signature pages continue]

                                       23
<PAGE>

                                     E. SUN COMMERCIAL BANK, LTD.,
                                     LOS ANGELES BRANCH

                                     By: /s/ Benjamin Lin
                                        ----------------------------------------
                                     Name: Benjamin Lin
                                     Title: EVP & General Manager

                           [signature pages continue]

                                       24
<PAGE>

                                   SCHEDULE A

                    SUMMARY OF MATERIAL TERMS OF ACQUISITION

                                 [see attached]

                                       25