Supersonic paying for 50/50 Fibre Line but receieve 10/5 connectivity

For the past year I have been paying for fibre 50/50 but whenever I do a speed test I get below 20/5Mbps. My mobile bill is running up having to wait more than a hour per call, how long can you be No. 1 in line? To date, none of their agents are able to assit or direct me to resovle this issue. Instead they put me on hold for another hour before the call get cut, this had been the routine for months. I am paying R1 000 per month for a 50/50 line but receievd around 10/5 line.