Bad service to the end

So apart from everything that annoys me about mtn customer service, I finally decided that keeping my contract with them is actually not worth it as I'm offline most of the time due to bad coverage. When i say i get annoyed i mean things like calling them a thousand times to have your voicemail switched off and never getting the result. In this case though went into a branch at greenstone mall to submit my cancellation, and was told that someone would call me promised call on Wednesday, it came instead on Thursday when I was in meetings at work. The person left a voicemail on my cell, informing that they need my email address and I should call 808. When I called 808, I was told that my email address is already there and that Retention probably needed it to advice of the termination amount. To this day I still haven't heard anything from Mtn regarding my request to cancel the contract. I was given a useless number that's supposed to be their Retention departments number. I went to greenstone branch and was given another useless number. It seems as though this Retention department of theirs forcibly retain customers with this snotty attitude as they cant be reached. Assistance pls