Due to be flying CPH - LHR - BOS today. Ticket booked via AA (i.e. 001 stock). Both flights are BA codeshares. BA812 [LHR - CPH] and therefore the first flight of the ex-EU, BA813 [CPH - LHR] has been cancelled this morning. As it was a B2B I am at Heathrow already. I first, incorrectly, rang BA as I assumed the flights being with them and it being their cancellation they would deal with it. As it's an AA issued ticket that is obviously incorrect.

I'm currently on hold with AA still trying to sort this. Apparently they won't just drop the CPH - LHR leg with their reasoning being "it's a British Airways cancellation". Not entirely sure what that means.

What are my options? If I don't get anywhere, I will HUACA however I've been on the phone for over an hour already.