Extremely Slow internet speeds

My company specializes in electronic repairs and IT support. We have been a loyal customer of Openweb's since 2007. We had an uncapped 4GB Gold account at around R800 P/M excl. ADSL line rental. I was told that this is best for business accounts as it doesn't get throttled as heavily. About 6 - 8 Months back the line speed became so bad that certain websites had to be refreshed four or five times to get them to open with constant DNS errors. After numerous support requests the issue was not resolved and I decided to move over to their so called 4GB uncapped unsnapped account at just over R600 P/M. The same issue is still there. It gets so bad that at times one can download 1Mb in around 2 - 3 minutes. their support staff is never available and will always call you back which 75% of the time does not happen. The line is definitely shaped to the point where it becomes unusable. The line speed issue usually disappear at around 17:00 in the afternoon, when most ISPs stop throttling their lines. This is completely useless for us as it is a business line. It is with a heavy heart that I recommend anyone wanting to sign up with an ISP to steer clear of Openweb.