Degradation of Service

My current ISP and line provider is Telkom. I am on a uncapped ADSL 2 meg line. I have had my line speed drop from a full 2048 kbps to 1600 kbps the to 1400 kbps and now to 1200kbps all in the course of a fortnight. The upload rate has also been cut in half, down to 250 kbps. I complained to Telkom after the first speed reduction and a fault ticket was opened and subsequently closed 24 hours later stating the fault was rectified, however it was not. After the drop to 1200kbps line sync speed, I have opened another fault and requested and engineer to visit the site, however 1 week later and no response from Telkom. I called in again and explained my situation but I was simply told that a ticket is open and I should wait. There has been no time frame given to me and I am paying for a service that I am not receiving and is practically unusable.