We are new to Xbox... we bought a secondhand Xbox 360 for the kids for Christmas, set it up, bought some games and then I put a set top box on top of the Xbox and it overheated (doh) .... so, we bought an Xbox One in the boxing day sales. 

In the weekend I was able to buy some games from the Xbox NY Countdown, it was an easy process, pretty much one click and it downloaded onto the Xbox 360. I'm trying to buy more games now for the X1 but it is asking me to add a credit card (there is already a credit card on the account). 
When I add a new credit card it says I can't use that payment method. I've missed out on a few cheap games we were wanting to buy ($5 Lego games)

Has anyone else successfully bought from this sale? 

We can buy games directly through the Xbox One with no problem, but the prices are horrendous compared to this sale.