Continued poor ADSL and customer support

I have had extremely slow internet performance for a few months now. A couple of days ago, a Telkom technician came through and concluded that it was an exchange issue and told me that he would pass it over to the relevant group. The internet is now worse than it was at the time. Someone from Telkom phoned me today to follow up and I explained the situation to him. He told me that he was going to phone me back, but he never did. I am so sick of this, this is the third time that a technician has come through and nothing has changed even after they confirm that there is a problem.