I booked a flight out in first to Sin and back from BKK in April on the 50% offer. I also used the Amex voucher. When the BKK return flight was cancelled someone at YouFirst changed my return to SIN - LHR. This showed for months in my MMB but was apparently never actually ticketed. BA called today to say that I can either move to to a Malaysian airlines flight back from BKK or pay full Avios for the rerouted return (only if there’s availability). Neither option is available past the end of June. They said the earlier agent had made a mistake and should not have allowed the change, it was only because the Malaysian Airlines contract wasn’t in place at the time of my rebooking. Do people think this is reasonable and I was just lucky first time round?