Hello! I'm sorry to hear you're having issues with your payment options.
There are currently a few options we could try. Firstly you could try setting up a Paypal account to associate with purchases if the credit card is not working. Secondly, you could purchase Xbox credit cards in the forms of '£15, £25 or £50' and then redeem
them on your console using the code on the back of the top up card.
Alternatively, you could try adding a credit card via the Xbox website,