Over billing and poor service

I have had it with MTN. I have been at all service centers all over western cape seeking help and the service is just plain sloppy! I have been with MTN for years now and since last year so many issues had risen. I get over charged every month. Last year i had a bill of R5000 and this months again R3000. My service get suspended without any warning. I dont get a phone call, not a text no nothing. I dont get any text stating the outstanding amount for the month. Today is the first, and so i get suspended yesterday. When i go to the service centers no one can tell me why my bill is so much. I pay you an amount of R1851 yesterday and all text i can get is that there is an amount of R1300 outstanding. HOW IS THIS EVEN POSSIBLE??? I call customer service and after about 5 mins of holding the line just dies and how are they always \ experiencing high call volumes". Yesterday im at willowbridge mall...how do they help...by calling 808 putting my phone down and then helping another customer??? Tygervalley and canal walk aren't any better help! Your service is for utter **** and you are making me poor without any explanation of where these amounts come from """