I am trying to change the return of my Amex Reserve companion cert flight booked in first class (I) with a reserve companion cert.

The agent tells me that the reissue desk is telling her that it can't be done because the flight I want also needs to have LUTV main cabin space in addition to the I or Z space. The published rules don't say this. The rules say that LUTV is needed for main, and LUTV and W for C+, but only I or Z for first class.

Anyone run into this issue before? Am I reading the fare rules correctly?

"Changes are subject to the rules of the fare purchased and are subject to seat availability"

"Tickets are only available in I and Z classes of service for First Class travel, and only available in L, U, T, X, and V classes of service for Main Cabin travel. For Delta Comfort+ travel, tickets are available in W and S classes of service, but only when L, U, T, X, or V classes of service are available in the Main Cabin."