Mtn issues

I've been trying to cancel my mtn wifi contract for a few months now because their network is really bad and slow and it doesn't even work most of the time and every time I try to call them or go in store, they say my contract hasn't expired as yet, I need to call to cancel it on the 25th or I should cancel it in July when it ends. I tried calling mtn today, and I've been on this call for 25 + minutes, and no one even bothers to pick up calls... Literally one of the worst service providers I have ever come across and I've never had a problem with mtn before ( except for the network issues), I will also not be using mtn anymore nor will I recommend their services to people I know.