MTN ****med me a long 6months

I took a data deal at Mtn Tygervalley mall Cape Town the deal was uncapped at 10mbps@R499 off wish it did not work in my house then I contacted them looking for a solution they suggested that we upgrade to 20mbps I agreed but it also didn't work. I contacted their coverage help desk they did their investigation and they issued a letter confirming that there is no coverage in my area so the deal has to be cancelled so it was cancelled. But now they are refusing to refund/credit my account for the month that I have paid for. I have videos showing how difficult it was to watch anything using that data. They also sent me my usage analysis off which it shows that I used +-20052 bytes per day. On a 20mbps deal. This is so not fair I did speak to sale consultant, store manager both after seeing the videos they agreed with me but the Area manager said declined my credit. Now am using Telkom data and its working perfectly