I don't know for sure, but I suspect you'll need to Cancel Subscription and then resubscribe. I know thats the route you have to take if you want to change your billing period for example, but I'm not sure in the case you give.
Another option might be to check you Billing summery, does it have an Add Credit card option? (mine has change and remove).
No it doesnt, but thanks for the help. I'll change my billing subscription, 'cause I'm on timecards at the mo
Does anybody know how to add Credit card details onto an account which uses timecards?
I know it sounds stupid, but I'm dumb.