Remove Payment Method

I'm trying to remove the card that is linked to my account but I keep getting a "restricted" message.  I've already been billed for a month of service after I cancelled my account and want to make sure it doesn't happen again.  FYI, I called customer service about the billing issue on 1/15 and was assured I'd receive an email within 24 hours with a refund amount and have yet to receive said email.