Hello FK I recently bought a 3 month code, and when you try to redeem it, it says it is a real code and you can take it. But when you click redeem code, it either gives you an error of some sort or says your account billing microsoft account has been banned. btw, this is when you enter the code on xbox. so all you have to do is,
Type this code in on xbox -
TMCH3-FB7XK-VCJT2-WBK2M-9D78X
Get the error message
Call xbox and tell them you are having a problem redeeming a code.
Tell them you tried on the xbox, website, and tell them you even deleted the profile off your xbox and redownloaded it again.
Then make up some dumb story about not being able to play for a while, or like say that you will only be able to play for 2-3 days and i really want to play xbox. [THIS PART CRUCIAL]
Keep insisting on the above step.
They should give you a reference number if you did it correctly, or ask you for a contact email to send you the code.
Your welcome for the free method