Upvote:6
What to do?
Read the fare rules of your ticket. These spell out the exact rules conditions for changes, cancellations, refunds, change fees, vouchers etc and these vary a lot depending on the exact type of ticket that you bought. There is no such thing as a "normal" ticket, they all are different.
Chances are though, that the Air France agent did exactly that and that the rules determine that you can't make that change. If you find otherwise, you can call them again and show them your fare rules.
If you can't do the change you can consider cancelling and making a new booking. Whether that's reasonable or not depends, again, on the fare rules.
You actually got lucky that Air France talked to you in the first place, they could have just sent you back to Expedia.