No Mtn response on data usage stronly disputed

I have a R 69,00 pm Mtn data contract since 13.09.2014( 1 Gig + 1 Gig). Usage has been within the contract amoun, but suddenly soared to R542,95 in August and R 2 365,69 in September 2015. First querie/visit to Mtn was on 5 October 2015. I was promised an investigation with e-mail response and, on Mtn's advice, my usage was capped at 1 Gig. However, I was also not informed that I shall loose my 1 Gig (Night). This I found out much later. Six weeks and four queries/visits to Mtn later (each visit a 80 km return journey) I have still not received any response on the enquiry in which I strongly dispute the above amounts that I was debited with.