Who are "they" who keeps testing my line with no resolution?

As everyone else have experienced over the years, once again Telkom does not care about its customers. I pay for a 20Mbps VDSL internet line, which, since end of January only connects at speeds varying from 3 to 6 Mbps. In addition, it keeps dropping the connection alltogether resulting in having to restart the router before it will reconnect. I reported the fault on February. A few days later they sent me a message to say it is fixed. Well it was not. Same problem continues. I reported it again on 15 February. Every time I follow up I get told "they are busy testing the line". I has been 3 weeks since the second report, and "they are still busy testing the line". The best part is it is impossible to get a phone number for any person who might actually be in a position to tell you a bit more than "they are testing the line". Once again my query is escalated and.... oh, I guess it will be ignored like everyone else.