MTN *****ing from me and I have been a customer for 17 years

Been a client for 17 years. Went into a store 3 months ago and requested an upgrade - was advised I had one in January of this year. Phoned the ***** unit - sent the sworn affidavit - certified copy of my identity document. Sent it to 3 people. No response. I contacted the upgrade department myself and I was informed that I took the upgrade out telephonically and MTN managed to deduct February and March instalments however April May and June were blocked by myself BUT I am paying for those blocked fees. This is an absolute disgrace and no one has contacted me since - like seriously - a customer for almost 20 years and you do this. MTN you suck