There's a lot of prepaid cards you can use, when you go the T3Fun website it gives you several options.
I personally use ultimate game cards.
Although it is difficult to redeem them since the only ones around here are 20$ and T3 doesn't have a 20$ option.
You'd have to email playspan to manually purchase your T-coins with the remaining money on that one prepaid card and it's just a huge clusterfuck so moral of the story use a credit card.
Have a nice day.