VODACOM PHONE CALL CUT/ DROP & BAD SERVICE

I have been a client with Vodacom since 2002. In the last year or so, everytime I receive or make a phone call the line drops. I am using my number for work and speak to clients and have lost clients due to this. I have contacted Vodacom many times (about 6 different times) to sort this out and all they say is "the request is being addressed". They say they will call me back, but all they do is send an SMS saying they are addressing it. How many weeks do they need to fix a service I am paying THOUSANDS of rands for????? I can not accept this and will NOT RECOMMEND VODACOM!!!!!!!!!!!!!!!!!!!!!!!!!