Over R5000 Over-Billed Since Cancellation

I was assured this contract would be cancelled in April due to lack of signal in our area. A booster made no improvement and technicians refused to install due to that. Over R5000 has been billed since this time despite me having to buy a new package from another provider that could service our area. I'm going to take this further, with a lawyer or another complaints commission if this is not resolved and refunded by mid-next week.