This is for those of you that have had problems adding payment methods or purchasing MS Points.
I had this problem for over a year and had tried just about everything, and nothing worked. I have finally found a fix that worked for me, so I thought I would post it here instead of replying to everyones seperate threads.
Alright so finally I have fixed this issue and am now able to buy MS points
again! I still can not use paypal as a payment method but I can add a card so
that is fine by me.
What I did to finally get it working was change my billing contact email on xbox.com to a new email,
different than my WLID that is tied to my gamertag, and now it works fine.
Post here if this helps you, if not I will try my best to help you get it sorted.