FIRST AMENDMENT TO AMENDED AND RESTATED INVESTOR RIGHTS AGREEMENT

EXHIBIT4.3

F IRST A MENDMENT TO A MENDED AND R ESTATED I NVESTOR R IGHTS A GREEMENT

T HIS F IRST A MENDMENT T O A MENDED A ND R ESTATED I NVESTOR R IGHTS A GREEMENT (the “ Amendment ”) is made and executed, dated for reference purposes as of February 12, 2004, and effective with respect to each provision hereof as of the “Effective Date” specified for such provision in Section 5.1, below (the “ Effective Date ”), by and among C ALL W AVE , I NC ., a California corporation (the “ Company ”), and each holder of outstanding shares of the Company’s Preferred Stock (each, an “ Investor ”), with reference to the following facts:

R ECITALS :

A. The Company and those persons (the “ Prior Holders ”) who then held outstanding shares of the Company’s Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock, Series D Preferred Stock, and Series E Preferred Stock (collectively, the “ Prior Series ”) previously executed that certain “Amended and Restated Investor Rights Agreement” dated as of May 31, 2001 (the “ Rights Agreement ”), pursuant to which, inter alia , (i) the Company granted certain registration rights to the Prior Holders, (ii) the Prior Holders agreed that their shares of Company capital stock subject to that Rights Agreement would be subject to a “market stand-off” restriction, and (iii) the Company granted certain information rights to the Investors.

B. Concurrently herewith, each person that is executing this Amendment as an “Insight Investor” hereunder (each, an “ Insight Investor ,” and collectively, the “ Insight Investors ”) is purchasing certain shares of the Company’s Common Stock and certain shares of the Company’s Series E Preferred Stock (the “ Series E Preferred ”), and the Company is agreeing that the Insight Investors hereafter may exchange such shares of Series E Preferred for shares of the Company’s Series E-1 Preferred Stock (the “ Series E-1 Preferred ”).

C. In connection with the Insight Investors’ purchase of the shares of Common Stock and Series E Preferred Stock, the Company has agreed to amend the Rights Agreement in order to confirm that:

(i) The first date for exercise of certain demand registration rights under the Rights Agreement shall be deferred until June 30, 2007;

(ii) As of the date on which any Insight Investor first purchases any shares of the Company’s Series E Preferred, such Insight Investor shall become a party to the Rights Agreement, and thereupon (A) may exercise thereunder with respect to the shares of Series E Preferred that such Insight Investor holds (and any other shares issued upon conversion or exchange thereof) all of the registration rights granted in Section 2 of the Rights Agreement, and (B) shall be entitled to the information rights set forth in Section 3 of the Rights Agreement; and

(iii) As of the date on which this Amendment has been executed by all of the parties to the Rights Agreement, the Insight Investors shall be entitled to exercise with respect to the shares of Series E-1 Preferred (and any other shares issued upon conversion or exchange thereof) that they may hold the registration rights set forth in Section 2 of the Rights Agreement.

C. The parties have agreed to execute this Amendment in order to memorialize their understandings with respect to the foregoing matters.

A GREEMENTS :

N OW , T HEREFORE , the parties hereto, intending to be legally bound, do hereby agree as follows:

1. A MENDMENT OF R EGISTRATION R IGHTS

1.1 A MENDMENT OF S ECTION 1.6 . Section 1.6 of the Rights Agreement is hereby amended in its entirety to read as follows:

1.6 “ Preferred Stock ” means, collectively, the Company’s (i) Series A Preferred Stock, (ii) Series B Preferred Stock, (iii) Series C Preferred Stock, (iv) Series D Preferred Stock, (v) Series E Preferred Stock, and (vi) Series E-1 Preferred Stock.

1.2 A MENDMENT OF S ECTION 2.1 . Clause “(i)” of the first paragraph of Section 2.1 of the Rights Agreement is hereby amended by deleting “April 30, 2002” therefrom, and inserting in its place the following: June 30, 2007.

2. I NFORMATION R IGHTS TO I NSIGHT I NVESTORS . Notwithstanding any provision of the Rights Agreement to the contrary, and as an inducement to the Insight Investors to purchase shares of the Company’s capital stock, the Company hereby agrees that each Insight Investor shall be entitled to all of the information rights set forth in Section 3 of the Rights Agreement.

3. J OINDER BY I NSIGHT I NVESTORS . Each of the Insight Investors is hereby added as a party to the Rights Agreement, effective as of the Effective Date set forth in Section 5.1(a), below, and hereafter:

3.1 S ERIES E P REFERRED R IGHTS . May exercise with respect to shares of the Series E Preferred held by such Insight Investor, all rights conferred upon “Investors” in the Rights Agreement with respect to shares of Series E Preferred;

3.2 R ESTRICTIONS . Shall be subject to all restrictions imposed upon the “Investors” therein (including the “market stand-off restriction” described therein); and

3.3 S ERIES E-1 P REFERRED R IGHTS . May exercise from and after the “Effective Date” specified in Section 5.1(b), below, with respect to shares of the Series E-1 Preferred held by such Insight Investor, all rights conferred upon “Investors” in the Rights Agreement with respect to shares of Series E-1 Preferred.

4. A MENDMENT OF R IGHTS A GREEMENT

4.1 D ELETION OF S ECTION 2.11 . Section 2.11 of the Rights Agreement is hereby deleted in its entirety.

4.2 A MENDMENT OF S ECTION 4.7 . Section 4.7 of the Rights Agreement is hereby amended to read as follows in its entirety:

4.7 E NTIRE A GREEMENT ; A MENDMENTS . This Agreement represents the entire understanding of the parties regarding the subject matter hereof, and supersedes and replaces all prior and contemporaneous understandings of the parties regarding such subject matter. Any term hereof may be amended, waived, discharged or terminated by a written instrument signed by the Company and the holders of a majority of the Registrable

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Securities; provided that no amendment or waiver shall be adverse to the rights of any one or more holders of Registrable Securities in a manner different than the manner in which the rights of other holders of Registrable Securities are affected, without the written consent of each such holder whose rights are affected in a more adverse manner. Any amendment or waiver effected in accordance with this Section shall be binding upon each holder of Registrable Securities at the time outstanding, each future holder of all such securities, and the Company.

5. M ISCELLANEOUS

5.1 E FFECTIVE D ATE . This Effective Date of this Amendment shall be as follows:

(a) I MMEDIATE E FFECTIVE D ATE . The provisions of Sections 1.2, 2, 3.1, 3.2, and this Section 5 hereof shall be effective as of February 12, 2004.

(b) D ELAYED E FFECTIVE D ATE . The provisions of Sections 1.1, 3.3 and 4 hereof shall be effective as of the first date on which each Investor that is a party to the Rights Agreement has executed this Amendment.

5.2 C OUNTERPARTS ; F ACSIMILE S IGNATURES . This Amendment may be executed in counterparts, each of which shall be binding upon the signatories thereto and all of which, taken together, shall be treated as one and the same instrument, binding on each signatory thereto. A copy of this Amendment that is executed by a party and transmitted to any other party by facsimile shall be binding upon the signatory to the same extent as a copy hereof containing that party’s original signature. Any party executing this Amendment by facsimile agrees, upon the request of any other party, to execute and deliver a counterpart hereof containing that party’s original signature.

5.3 R ATIFICATION . Except as expressly modified by the foregoing Sections hereof, the Rights Agreement is hereby ratified and confirmed and remains in full force and effect.

[ Signatures appear on the following page .]

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I N W ITNESS W HEREOF , the undersigned have executed this Amendment, effective as of the “Effective Date” set forth above.

“C OMPANY :”

[ Signatures of Additional Investors appear on following pages .]

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“I NSIGHT I NVESTORS :”

[ Signatures of Additional Investors appear on following pages. ]

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[ Investor Signature Page to First Amendment to Amended and Restated Investor Rights Agreement .]

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[ Investor Signature Page to First Amendment to Amended and Restated Investor Rights Agreement .]

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[ Investor Signature Page to First Amendment to Amended and Restated Investor Rights Agreement .]

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[ Investor Signature Page to First Amendment to Amended and Restated Investor Rights Agreement .]