MTN, BAD CUSTOMER SERVICE

6 months ago , I started an telephonic contract with MTN for a home WIFI route. I tried to connect the router and it did not work, I called the customer service line, they told me someone will be sent to help with the installation. I waited a whole month, no one was sent, I called again, same thing again another person is going to be sent. I ended up purchasing another router from another service provider. Now I have been struggling to cancel my contract with MTN, I have called countless of times, I keep getting transferred to different departments, until they hanged up the call. I went in-store to the Hemingways Mall centre, they told me that they could'nt assist me with the cancellation it can only be done telephonically, I asked if I could use one of their phones they told me none of their phones work. I need help cancelling this contract, cause now MTN is charging me for a service that I have never used.