incorrect billing

I have a MTN contract due to the fact that nashua mobile had closed down and MTN had taken over their customers.i have upgraded to a R380 ...top up contact .I have been billed R600 for march and April. I called MTN customer sgervices for the past 2 months and I was told the problem will be solved and that I will be credited because I was billed for things from my orevious contract and other things that I should not be billed for.nothing was done about the problem so I went back to the MTN umhlanga branch to speak to management. months have gone by now and the problem is still not rectified.for may this month I got billed and debited R700 after been told the problem will be rectified.to top this all this morning I wake up to a suspended phone line.i am highly disgusted with mtn services and I cannot wait for this contract to end.i will never be taking or recommending MTN contracts to anybody. I am very dissapointed with MTN services.