Being billed for a package I did sign for

My contract stipulated the package that I signed for however my account has been credited with the wrong package for the 2nd month now. After I received the statement of R959 in April I went to the store to find out as to how did my bill get to such amount for a Huawei P smart on mtn made for me s@R249 that was on special on the March catalogue, the very same lady(Kholiwe) who did my contract was not able to give me clarity said she will log a query and asked me to not reverse the debit order. I then contacted the call Centre to get a breakdown of the invoice and I was told that I was billed for a wrong package(mtn made for me m) and a connection fee of R132 of which I had paid at the store the day I collected the phone. I was told to go to the store to query with them but since I didn't get any help when I went there I decided to call them and I spoke to Kgotso who said I must email him a copy of my contract so he can assist in resolving the issue and I did what he asked. I haven't received any feedback from Kgotso or the store. I have been querying with customer service via email but all I get is different reference number and that my query has been sent for investigation. Now I received the May statement with the same amount due and at the end of the month my bank account will be debited with such a huge amount I didn't signe for. I need to be refunded my money and want mtn to send me the correct statement. If I don't get refunded and still debit my account again I will the be forced to reverse the transaction and terminate the contract.I certainly regret taking a cell phone contract with mtn