Pathetic ADSL Service from Telkom

I app**** for a 20MB Line from Telkom, they said no problem and they installed it. But after I got my line, they told me that I am 2.8km from the exchange. My line was fine at first but then started to degrade as time went by. I logged many calls, Technicians came out and nothing changed. I asked Telkom for a downgrade, they told me that someone would call me by the end of business day and someone did phone me a week after that. After a long struggle on the phone with someone who couldn't speak clearly, he told me I need to pay my account to be able to downgrade. That was on the 3rd of July. My debit order went off on the 25th of June and my account is paid in full. Telkom accounts did say I will be credited because of my problems but I paid for a full 20MB Line and I only got 7-8MB's on average when I am lucky. Before writing my review, my line is down to 0.5MB's and I'm paying full price for a 20MB Line. I think it would be better if Telkom would just cancel my account and I will find better service elsewhere.