ADSL nightmare

I have had an ongoing problem with my ADSL speed the last few months. I get 4meg speed for a few days, then it drops to 2.5meg again. After Openserve re-loads the DSL port, the cycle begins again. They have tested the line up to my house and said they cannot find a problem. I have replaced my indoor cabling, filter and ADSL modem, still the same problem. My modem syncs at 2560kb/s again. Are there no more brainpower left at Telkom/Openserve anymore? I reported the line again over the weekend and this afternoon I got an SMS saying that the fault has been resolved. IT HAS NOT BEEN RESOLVED, I AM STILL GETTING 2.5KB/S SYNC WITH THE EXCHANGE. CAN SOMEBODY PLEASE FIX IT?