MTN **********ly debiting my account and won't reply to my emails

I paid off my two year contract with MTN in full and gave 6 months notice with confirmation received in writing from MTN "customer care" (ha ha) that the last debit would come off my account in June 2017. I am now living abroad and receiving no services from MTN but they keep debiting my account each month. I've sent over 25 emails requesting that they refund me and stop debiting my account, or send me the contact details of the ombudsman. No response to these requests. Funny that MTN won't reply to my emails and yet keeps treating me as a customer by taking my money (oh, yeah, I forgot - that was what it was always like to be an MTN customer). I have to keep manually reversing these ********** charges from abroad because I'm not in a position to change my bank account to try and escape from MTN. Can any one give me the email address of the appropriate ombudsman? And if anyone out there is considering signing a contract with MTN and handing over their bank details: just don't do it! I've told them repeatedly that they are not authorized with debit my account and they just keep doing it. That's theft, I believe? (Btw, this form requires me to give a star rating to MTN so I've selected one - they don't deserve more than 0)