Payment method declined

Can someone please help me, I recently ordered a new debit card from my bank but every time I try to change and update my payment method on apple I'd it always says payment method declined, it's not a problem with my bank I've already spoken to them, I've tried updating my details on I tunes on computer but to no avail, it's really frustrating, I can't even get free apps or update apps I've already paid for.....aaaargh