We had a horrible flight experience with United/Air Canada and Alitalia.

The ticket was booked on an Alitalia ticket stock, routing Toronto-Milan-Newark-Toronto. The return flight was changed by Alitalia in Milan, updated in both the Alitalia system (for MXP-EWR) and the United stystem (for EWR-YYZ). In addition to that, I got an updated print-out and my ticket was stickered, flight status was "OK". MXP-EWR was in D and EWR-YYZ was in Y.

* United in EWR had us to check-in with Air Canada because AC was the operating carrier.
* AC refused to accept our tickets because it was stickered. They said "no stickers on international tickets".
* AC sent us to AZ.
* AZ were unwilling to help us because "no stickers" and because of "fare restrictions".
* We then went to UA because we were confirmed on a UA flight. UA refused to take responsibility because "we will not receive any money from this flight".

To make the story short: None of the three airlines wanted to accept our valid ticket and we ended up buying three new one way tickets from United for exactelly those flights that we were holding valid tickets.

A call to United gave me the result "Sorry for the inconvinience, please deal with AZ. No refund possible".

What would you do in such a situation? From whom shall we get the money back? Which steps are we going to take now?