MTN is holding me hostage to a contract

I have had a contract with mtn for the past 24 months and due to their poor network, failure to attend to queries and their billing problems I have decided to merge from contract to pre paid. I request for the contract to be merged a week before the contract expired and I was told that the request was sent through and I would be merged on the 20/09/2015 since then I've been calling and all I was told was that it was being processed. I was later told I had R28 outstanding and that's why this account could not be merged, I paid the amount outstanding and sent the proof of payment to 2 mtn agents on the following addresses: [Email Removed] and [Email Removed] and till today I'm still trying to get my account to be merged. this is ridiculous because I have served the 24 months I signed for and if the service I received was worth the money I pay I wouldn't request a merge <br> now they are basically dragging on the process so they can keep me on the contract that I refuse to be bound to this is like holding me hostage because I'm being held to a contract against my will and after I followed the required process to cancel the contract