Telkom not able to fix my line!

Hi there, I have an open fault with Telkom on my Telkom line. For the past few weeks I've been complaining about slow speed. I'm on a 10mb contract but constantly only get 0.48 - 1.2mb. Which is totally unacceptable. First they told me my line could only handle 4mb. But on Saturday a technician put the port at the exchange up to 8mb. On Saturday and Sunday I go a constant 6mb download speed. But Yesterday afternoon it was back to 0.57mb ... I phoned Telkom and queried this, the call center agent Nicky reset the port and then after that NOTHING wants to work anymore. She was going to phone me back to let me know if a technician is available, but never called me back. I'm an IT contractor and I NEED this line up or otherwise I'm losing working hours. This is a serious issue. I'm also fed up paying for a service and a speed I don't receive!!!! Please can this be sorted out ASAP.