Vodacom, poor after sales service

I have taken a sim data contract out as fiber was not available in my area. I was told that I have good coverage in my area, only to find as time progressed it became terrible. I have called, log calls and been in several stores to request assistance. It's been several weeks and only received a cold shoulder. I am at a point that I would like to cancel the data sim contract, of which I have been told is also not possible.