Slow speed and WhatsApp bit is so useless

When I first set up my 50mbps up and down the highest I ever got on testmyspeed(as recommended by webafrica) is 17mbps down and up. I then upgraded to 100mbps up and down and the still the highest is 20mbps up and down? I have a direct line to my PC and I check the speed daily(just to make sure it wasn't a technical problem at the time) your WhatsApp bit is possibly the most useless thing I have encountered in my life(been waiting for the past week to be connect to someone. Your call centre possibly the 2nd worst. Please contact me to sort this issue out.