Webafrica not giving the speed I pay for

I have been fighting with these people for weeks now about my fibre speed and everytime they saying they checking or I must reboot my modem I'm paying for a 75mb line but my speed is not close to that with 1 device connected and these people keep telling me the same thing over and over all I ask webafrica is for use to sort my speed out I'm paying R850 a monthly and not even getting the speed I'm paying for your company is the worse to try and get hold of I want answer and I'm getting more questions from your people use don't even call that's how bad your service is