Speed and service poor

I've upgraded my line from 10mbs to 20mbs, but is only getting about 12mbs. I reported the concern on 6 Feb but still not resolved. I'm phoning every day but no luck. A technician phoned me on the 24 Feb (Sunday) and told me he will be there the next day. I phoned him on 25 and 26 Feb but he did not pick up. I phoned Telkom every single day but no luck. I was then told that there is no technician assigned to my concern yet after a technician phoned me a few days ago. For nearly a month now I did not get my required speed, but I'm sure I will have another with Telkom because they will charge me for a 20mbs line. Can you please urgently resolve my concern