Cannot cancel contract

The amount of poor service received from customer care and retentions is pathetic. I have been trying for months to cancel my contract with no luck just excuses and them sending me back and fourth. My account went from R300 to R1900 because someone changed it after I requested it to be canceled and converted to prepaid. I need a manager to contact me asap and cancel the contract and convert it to prepaid. I am tired of calling constantly and sending emails with all my requests being ignored. I will not recommend MTN to anyone and they signal is very poor and their service. I will contact my lawyers regarding this matter is MTN does not assist