Bad service

I have been trying to contact mtn from Friday since my contract is coming to an end to let them know I won't be needing their services anymore but they don't respond I have been on the line for forever on Friday it was 20 minutes and today 15 minutes, I'm not getting any response firstly this contract was supposed to be a 20 gig day and 20 gig night for R230 I went from pillar to post with no assistance from their side and have since accepted it but now that I want to cancel I'm also not getting any help, what does one have to do to be assisted by mtn?