I assume it's one of those gift cards? The reason you wouldn't want to do that is that they charge you a fee every time you use it unless you spend the entire amount at once.
So if you do a bunch of small transactions you actually get way less than the advertised value....
They never charged a fee for me, either way it's my only option to use.. since I can't charge it on the bill... (I don't pay for the bill) soo.... the only other way I know would be the prepaid credit card. Would it work though?