I was in the
EXACT same situation as you. My app had reached them on the 18th of March and then my CC had to be closed due to fraudulent activity.
So I contacted them and their rep gave me incorrect info, telling me that I should send a letter with the old and new numbers, explain the situation and sign the letter. She seemed confident and emphasized over and over that the signature was very important. So I did not suspect that I was being mislead. So I sent the new info on April 10th and waited patiently.
Then on ~ June 6th, when my app was due to be processed, they told me that my app was declined because I had not submitted the new info on
their standard form, even though the info was exactly the same. They asked me to fax the new form and
insisted (not once, but on 3 separate calls) that it would go back in line and take another 3+ months, leaving me in a panic!! (even though I had sent a 2nd set of prints on April 10th, just for safety)
Anyways, to make a long story short, I ended up faxing them the info on their form and wrote a compelling letter explaining my situation with Canadian immigration and the possibility of not getting a second extension. After exactly 2 days my new credit card got charged (the phone reps were still insisting that my file has gone back in line for the 3+ month wait :
). In spite of the charge I was not sure if it meant that they have processed my app. So then I called them after another 3 days, and the rep said my PCC had already been mailed out!! Now it has already reached Ottawa on the 22nd.
So, considering my experience I am positive the reps have no clue what their talking about most of the time. Just write them a really strong letter explaining why your card got declined and politely requesting them to make an exception and process your app. It worked for me. It would probably work for you as well!