suggest CALLING Commonwealth directly via phone; they should be able to help you 'on the fly'. You want to pursue this and ensure the credit line is shut down by that bank... if someone else has that card, they could be racking up more dollars as time goes on.
any chance you took out a credit card at a retailer and didn't realize that Commonwealth is really the bank behind the card? (if you have any other cards look closely at the back of the card or the statement..for example, Best Buy and Macy cards are issued by CitiBank, etc.)
good luck!
