Exhibit 99.(h)(xxx)

November 6, 2024

State Street Bank and Trust Company

1 Iron Street

Boston, MA 02210

Attention: Scott Shirrell, Managing Director

Re: Calamos ETF Trust (“Fund”)

Ladies and Gentlemen:

Please be advised that the undersigned Fund has been incorporated and registered as a management investment company under the Investment Company Act of 1940, as amended, and such Fund has established those new series of shares identified under its name on Exhibit A hereto (each, a “Portfolio”).

In accordance with Section 8.6, the Additional Portfolios provision, of the Master Services Agreement dated as of March 15, 2004, as amended, modified, or supplemented from time to time (the “Agreement”), by and among each registered investment company party thereto, and State Street Bank and Trust Company (“State Street”), the undersigned Fund, on behalf of its respective Portfolios, hereby requests that State Street perform certain accounting and fund administration services for its Portfolio under the terms of the Agreement, and that Appendix A to the Agreement is hereby amended and restated as set forth on Exhibit B attached hereto. In connection with such request, the undersigned Fund hereby confirms, as of the date hereof, its representations and warranties set forth in Section 4.2 of the Agreement, and, for the avoidance of doubt, acknowledges and confirms to State Street that the letter agreement dated March 31, 2006 (“Third Side Letter”) by and among certain funds in the Calamos Family of Funds and State Street shall also apply to each Portfolio, and the undersigned Fund agrees to be bound by all the terms and conditions of the Third Side Letter.

Please indicate your acceptance of the foregoing by executing this letter agreement and returning a copy to the Fund.

Information Classification: Limited Access

EXHIBIT A

Calamos ETF Trust

Calamos Nasdaq-100 Structured Alt Protection ETF – December

Calamos S&P 500 Structured Alt Protection ETF - November

Calamos Nasdaq-100 Structured Alt Protection – March

Calamos Russell 2000 Structured Alt Protection ETF – January

Calamos S&P 500 Structured Alt Protection ETF - December

Calamos S&P 500 Structured Alt Protection ETF - April

Calamos S&P 500 Structured Alt Protection ETF – June

Information Classification: Limited Access

EXHIBIT B

Appendix A

to

Master Services Agreement

Management Investment Companies Registered with the SEC and Portfolios thereof, if any

Information Classification: Limited Access

EXHIBIT A

Information Classification: Limited Access