That's not a debt - that's a point-of-sale. They're allowed to accept or refuse any form of payment there (at least under US law - UK is probably similar). The

That's not a debt - that's a point-of-sale. They're allowed to accept or refuse any form of payment there (at least under US law - UK is probably similar). The reason for the laws surrounding debt is to prevent creditors from purposefully holding debtors in debt by refusing to accept their payments ('Oh, sorry, you HAVE to pay me in this form, so I'll refuse your payment and instead charge you an extra day of interest, etc.)