Horrible service

What a (yet another) disappointing experience with Cell C. After 18 years with this service provider, I am trying my utmost to get rid of this horrible provider, but not even that can be managed by them. My previous contract was to expire end of February 2020, but I was eligible for an upgrade in December 2019. I updated my device, and it was made clear that I will pay my existing contract amount until Feb, when I will migrate to the new contract amount. For some reason Cell C decided to invoice me almost double my normal amount for February. When I queried this (after numerous disappointing tries to get hold of someone at their "lack-of-service-centre" , I was told that it was a mistake from Cell C's side, and that I can pay the full invoiced amount this month, and I might get credited for the excess next month. They could not confirm my update on their system. This is not an option, since after 17 calls to the call centre, I still don't have a revised invoice. Every single call that finally got through to the call centre, received a different answer - no one at Cell C can rectify the problem, nor come back to me. I've tried my utmost to cancel the upgrade and give 30 days notice, but no one at Cell C can even get that done. I urgently require Cell C legal to contact me, for the breach of contract, and potential theft case. This is ***** and I will not simply pay excess amounts made up by the provider, for something I did not ask for, nor ever received.