MTN voice quality really bad!

At the end of last year I moved my mobile phone contact to MTN due to a couple of reasons. Biggest mistake I could have made... I use my mobile phone for business and make a lot of calls daily and therefore also took a contract with a decent amount of voice minutes. At this stage I am paying for voice minutes I cannot use... When making a voice call I struggle to hear the other person or they struggle to hear me, waisting the minutes that we cannot hear each other and while it is happening multiple times daily I can basically say the service is rendered useless. I have complained to MTN a number of times and it has happend in 2 calls to them that the call drop and even gets so bad that their representative cannot hear me or I hear them. Still nothing from MTN, their staff does not even contact me back when this happens. I do not advise anyone to move to MTN, you will be disappointed in their network quality,