You could try signing up on Green Man Gaming or GamersGate. They both have a rewards program which lets you rack up store credit, or digital currency in the case of GamersGate, which you can use to buy games with. Just make sure that it's a Steam game you're buying first, and you'll receive a key to activate on Steam. Takes time, but you can make quite a bit through referrals.
Both websites also accept Rixty, a prepaid payment method that doesn't involve a credit card or bank account, although unfortunately GamersGate won't accept Rixty payments from SA. Not sure about GMG, seeing as they have disabled the Rixty payment option on their website. It has been that way for a long time.


. I've been with them for years, and I can never understand how any of the other banks survive, unless its purely due to consumer ignorance (and I mean this with no offense to other bank clients 