Dear microsoft about your Xbox live pass

I just have a question why the hell can't I buy 1 month of game-pass? The price in my country is R15,99 and I have R41,00 in my account but whenever I try and buy the 1 month it keeps promoting me to put in my credit card or a voucher? I have enough to
buy for one month why do I need to put down more money? Please is this a glitch or do you need the standard rate in your wallet before that function changes cause this is bs, I have more than enough money to buy for 1 month and you wont let me and you expect
me to put more money into my wallet? Please tell me this is a glitch or something or I will be a very dissatisfied customer.

:)