I tried using a prepaid credit card to buy Zen at one point didn't work. Basically when it checked it threw it back in my face.
Here is what worked.
Pay Pal green dot cards (but they want your Social security number)
If I was to buy anything more in this game it would go through steam. Why? Prepaid cards VISA/AMEX/Mastercards all have like a 5-6% charge associated with buying them. So a $200 card becomes $212 at check out. Furthermore the card I purchased didn't exactly like to work with their web system. Just save yourself the hassle goto a Game stop and buy a Steam card. Not sure if that works to get a LTS but under most circumstances the steam card is probably your best option.
That would be due to the fact that those are closer to actual credit/debit cards than gift cards. Hence, the provisions of the Patriot Act come into play. Therefore, they're required to get name, address, and social security number (since it's treated as opening a new financial account).
As to the person complaining about Walmart charging a fee for refilling the card, clearly states such in the terms and services (I've had a walmart prepaid so I know), and you can refill for free by cashing a payroll or government check and putting it on the card.