Capitec Bank account cleaned out!!!

An agent came to my shop and sold me a SIM card 11 months ago. I was very happy with it as you get Sunday spins and double data or airtime when you buy it. So when he came back, in uniform to tell me that he had a new upgraded SIM with extra bonuses etc so I let him change my sim card watching him all the time. He gave me back my original sim and left telling me someone's going to call me. After about an hour my phone died couldn't receive or make calls. I called unlimited and asked for a manager ..Devon .and told him what happened. He said the agent shouldn't have out in a new SIM...but he would try to fix my phone. He never once said take that sim out and put in your original one. Didn't warn me about going to the bank and checking on my bank acc. I had the Capitec app on my phone. I was not aware that they could get into my bank account with that sim. After about a day and a half, of me without a phone, and me phoning Devon all the time and asking what's going on..he said he had to deal with cell C and to take the SIM out....throw it away and insert original sim, then it worked again. Never once telling me what could have happened or to be careful....so I had no idea this sort of thing can clean out your bank account!!! I had a savings account which I try not to look at ..just keeping it there for emergencies ...so about a week later I go to check my balance and it's 0000!!!!! The whole lot has been withdrawn over a week...to a Capitec account and also to a checkers money market ..also airtime bought ...things I do not do!! 3-4k every day ...did not receive 1 message from the bank....not even on my land line or email!!?? No one knows my pin number... And I did not give it to anyone!!! What I want to know is..who is at fault here..Capitec or the Unlimited?? Capitec says I shouldn't have let him put a SIM in my phone...and they're not returning my money!! I'm saying how is it my fault if no one knows my pin number??? I am going further with this!!