MIgrating contract to prepaid

2015-October I went to MNT branch to enquire about migrating contract phone to prepaid,i was informed to call the call centre,few days later i called and made the request with call centre agent,to my surprise 2015 Nov i was billed again for the same phone i made a request about,i called MTN again to question about the request and i was informed that the agent probably did not capture it correctly,i was patient & requested again for the migration,2015 Dec again my account was debited,this time around i asked to speak to the supervisor bcos both agents i spoke to they are not capable of just logging this request correctly.Now its 2016 my account still gets debited.I can only come to 2 conclusion 1 MTN staff are *********** or MTN system are faulty.i'm not happy and this is really inconveniencing me to make calls everytime and don't get anything done with your company. get this matter sorted I need my money back and stop debiting my account. I hope someone will address this matter urgently, i not will not be using MTN as a service provide anymore, i have 2 contract and the last one will be my last i'm done. the number in question is ***