Difficulty cancelling contract

I am trying to migrate my current contract to prepaid from the date my contract expired, which was 27 April 2015. Reason: I currently do not yet need a new phone, and only use Afrihost data package. <br> I went to MTN service center in Century City the day this contract expired to authorize the migration, 28th of April, submitted a from, ref ***. Told me MTN would contact me to let me know that this has been done. <br> 2 weeks later I have not heard anything, so I went back, this time telling me that he could see it is in progress and that May's billing would be the last. Please note: every phone call to MTN customer care has been unsuccessful, as it was unavailable for months. <br> By the early June, still no word and still billed. Went in again, and this time they told me the application has never even started! So sent in another application, ref ***. Couple of days after it was successful. <br> My issue is I am sitting with a HUGE bill, due 1 July. 2 things: 1) billed a contract rate which includes the phone cost which is paid off, 2) Billing should have stopped in April when i app****. <br> I expect MTN to refund most of this bill, for me to ever consider a contract with them in future.