Very bad service and not feedback

I, suddenly after 15 years as a customer, receive an unexpected R3500 sms from mtn. I phone the call centre and query about it and I don't get the right information. I ask to put a limit on both my data numbers. After a month I get a bill to pay R3500. My question, why was the limits not put like I requested? I go onto mtnactive and I put the limits myself. Another month goes by and I receive another bill of R3500. I then call the call centre and request itemised billing for both my data numbers for the two months that the bill was so high. After 4 days of nothing I again phone the call centre and request it again. Only after a week I find itemised billing of my pay as you go number of the completely wrong month. I write an email as a complaint and after 5 days I had no feedback from the email. Again I phone the call centre and again I request the same things as twice before. Still waiting to see if the right info will be sent to me. I just need to find out where that R7000 of mine went and if it really was my mistake, after 15 years of nothing? The worst service ever!!!