That happened to me last summer. I had to rebook cancelled flights with British Airways multiple times to get home. In the end i was out over £15000 pounds worth of flights. BA offered me vouchers valid for a year in replacement. In the end i called my credit card company and disputed the charges. They wanted me to pay in the interim, I refused, and a few days later Amex credited my account. 90 days later they said BA had not disputed my claims on time, and I was therefore awarded the full amount.