Billing query

Mtn's service is nonsense I tell you. I signed up for that WiFi package that gives you 120gigs and I am supposed to be billed R269.00 but I've been charged R669.00 for the past 5 months, I've went to the benoni branch in lakeside mall and when they check on the system it says I signed up for the R269.00 package and absolutely no one can give me a solid explanation as to why I'm being charged this much money. I even went to the meadowdale branch where they informed me that my issue has been resolved and I will be refunded all the extra money I was charged and the was in January then in February they charged me that that R669.00 again. When I call the customer care, all the do is give me a ticket number which is a reference number which is the same thing I was given at the benoni branch. I've even been communicating with them by email and they keep telling me the same thing that my query has been escalated but nothing is done!