We can change your billing date by taking a pro rata payment by card to bring you upto that new date. If you give customer services a ring they should be able to sort it out for you.
The billing runs from the 5th to the 4th, is it possible just to lose 4 days and get the next month starting on the 1st?
Would save the bother of using a card, and not bothered by losing the cost of the 4 days.