Endless issues with adsl line

I'm based in witpoortjie.. I have a 10meg line which i have from December 2017.... From December 'til now, my line has been giving me constant issues where the line speed is way slower than it should be (clocked around 2mbps today) as well as the line keeps dropping... I've had technician after technician come to my house and "fix" the problem, only for it to continue a few days afterwards... Some technicians have told me that there was a problem at the exchange, others told me that the cable needs to be changed (which didn't happen) in really sick of this now... I use an IP phone for work and i can't talk to clients when they call because of this.. Line issue either too slow and i can't hear them or the line drops while I'm on a call and the call drops