bad customer care

my mtn contract ended in May. I have been trying to contact customer services to cancel the contract and change to pre-paid for two month now with out any success all I get is music playing in my ear no one bothers to answer the line. i went to one of their stores in Pretoria cbd and was told that they do not do any cancellation and they gave me an email address to send my cancellation to . I send an email to [Email Removed] on the 24/06/2015 and another one on 04/07/2015 still waiting for a response even now. I am very disappointed and angry with the bad service am getting from mtn. now I just want the stupid contract to be cancelled and have nothing further to do with mtn anymore.