Unresolved billing issue

My MTN contract ended about a week ago. Today i pay my account only to find out that my next payment will be almost R2000 instead of R1400 that it has always been. I call MTN and they tell me they moved my contract to Month-to-Month and are billing me double for the same package. I never received communication about this change, had I not gone to the MTN store today I would have never known. I’m very angry at MTN’s customer service, they don’t give a damn about customers. To make matters worse this is not the first time I’m having a billing issue with MTN, the first one was never resolved.