Without having a look at the actual T&C's of the credit card, i'm going to hazard a guess that there would be a wide clause there allowing them to be able to take the points back, or 'adjust' your balance to reflect what you accurately earned. That being said, a cogent argument could also be made that you should not suffer for the banks mistake, and they should bear the consequences of their mistaken actions. For example, if you were overpaid points, and then booked an award flight which you otherwise could not have taken without the overpayment of points, then it is highly unlikely that the award would be cancelled and points taken back, because then you'd be suffering a detriment at the mistaken representation of the bank/airline (that you had more points than you earned). If they just sit there and you do nothing with them, then that argument would assume less validity. Anyway that's the lawyer in me speaking. I'd be curious to see what other people thought.