Buying Minecraft...

I have been using premium accounts that people here in MPGH giveaway. But recently I decided to buy my own because I have a youtube and I have a friend which we are working constantly in his MC Server, problem, no matter the way I try to purchase the game, it keeps "denying" my purchase. I used my paypal, visa and mastercard and none of them worked. I also tried letting my friend to try and buy the gift code from his account (With my money;paypal etc...) and it didn't work either. I don't know if this has to do with anything, but I live in Puerto Rico.