Why can't i buy Microsoft Points?

the new map pack for Black ops called Annihilation came out and im trying to buy 800 MS points with my visa debit card ive been using for a while now and everytime i try to buy it a window pops up says "the selected payment could not be authorized please select another", idk whats wrong my card has money in it and i tried my dad's card too and his paypal and still it says the same thing AND in addition we went on xbox.com and tried to buy MS points on the internet and still same thing! wtf is happening how can i fix this?!?!?!?!!?