Using airtime incorrectly and not refunding or fixing the problem

I am on a contract where I get 10000 MTN to MTN minutes and 100 anytime minutes per month. This last month MTN has been using up all my anytime minutes when I call an MTN number and not the MTN to MTN minutes. When the anytime minutes are finished it won't allow me to call an MTN number, it says insufficient airtime. We have reported this to the call centre and were given reference number 1- ********** 1873. That same day I received an sms saying the query has been resolved. But nothing has been resolved. I have now had to buy airtime make calls and the call centre cannot advise when this will be resolved. I want my anytime minutes refunded and the airtime I've had to purchase refunded as well! This is totally unacceptable and a breach of contract!