I booked a RT flight that has 4 segments (2+2) online and now I want to add a stopover. I called up to request the change and since I booked the RT in different cabins Biz on the outbound and Y on the return, she couldn't change the reservation and said it has to go to "the back office".

Anyone know a workaround? I know this has been discussed for award flights, but this is kinda a different situation.

Edit- booking as a multi city books into a different fare class and is more expensive

Edit x2- is it possible to book a stopover (in Paris) on a RT ticket?