Unable to reach the so called contract cancellation

My name is Nematswerani Melta, i am so frustrated with the way i have been treated with Mtn. I had a contract with them and it has expired in jan. Since then i have been trying to cancel . I called 135 hundred times they keep on saying they are puting me tgrough and the phone get cut off, if it happen that i reached the the person helping does not have a system for old contracts.i went to the shop in protea glen they told me to call as they can not cancell.i do not know what to do anymore.need help.