Slow speed and poor customer service

I have installed fibre with Vox and Afrihost as my internet service providers. When I first installed the fibre the speed was 10 mbps download and 1 mbps upload, unfortunately we were not happy and decided to upgrade to 20 mbps download and 2 mbps upload. Vox on its own volution upgraded us to 50 mbps download and 10 mbps upload. The sad thing is at most all I get is between 1 and 10 mbps download and between 0 and 1 mbps upload. I have complained several times to Vox regarding this matter and all they tell me is switch the router off and on again, but the problem still persist. The speed got worse to the point where now we mostly just use cellphone data instead of fibre since it's not living up to the expectations. Vox had done a huge disservice to us and they can't even be bothered to send a technician to assist us. Their service is terrible and we pay for the speed that we never get and our complaints just fall on deaf ears.