Misleading Checkouts

Went on to make a booking, filled in my details and tried to pay. It kept telling me that it's incorrect and telling me to fill it in my details again. Must have filled in the field about 10 times before trying on a different browser and of course the flight had changed in price. Even though the flight was still in my basket, I couldn't checkout. Phoned the call centre and had a lady saying 'So what must I do?' repeatedly.