Huhe Bill and unprofessional Service

My Internet contract *** now migrated to prepaid the 22 July) of R320 per month for 5gig usage went up to +-R1700 per month from May-July. I have since then disputed this bill numerous times with no luck. My Wi-Fi is off most of the time and nobody at home using during the day. I'm the only person using it. e.g. for July invoice, I used my Wi-Fi for 2 days (23 & 25th Jun) only after work for few hours in that particular period and decided to pack it away just to see what's going on with this bill charges thing, I have been charged again +R1700, claiming that I reached my data usage limit by using 9gig for the said days/time. How do you explain such a huge bill/data usage? It's ridiculous. I need a detailed explanation and a proof for the data charged & for what. I have logged several calls through emails & calls to 808, with a bunch of references received and is already two months with no response. I was told it only takes 7 days to respond! To now, the matter isn't resolved and without any direction either. I also went to Boksburg and Midrand MTN with no help. Why should I struggle in getting response while you never in taking my hard earned money?