Q: issues with purchasing icloud storage

I'm uable to purchase extra storage for my icloud. Is anyone else having this problem. I've tried on my iphone, ipad and on my laptop. I do not have a credit card on file, I use itunes cards and am not sure if that may be the issue. I don't want to use a credit card, because a friend of mine used his for itunes and someone got a hold of it and charged up a good amount on it. Can anyone help me out, I want to purchase the extra storage.