Dont return money they took by mistake

In Feb 2015 I bought a domain at webafrica and all was well. For the next 3 or 4 months they kept taking R100 each month from my account. I phoned them and told them about the problem. After about a month they figured it out and told me they mistaked my name for someone else and the money was supposed to be debited from his account and that they fixed the problem. The month after that the same thing happened..I phoned again,after holding for more than 10min (like usual) i spoke to someone again and they guaranteed me the problem will be fixed. When I asked them when they will credit my money they said the person who they mistook me for must first pay them for them to refund me. As far as I see it this problem has got nothing to do with me,they must credit me. The rest is their mistake and their problem. They told me it would be sorted out in a weeks time..but here we are again 1month later and still NOTHING. Not a cent,not a word