Afrihost poor service

I have a fixed LTE package from Afrihost because there is still no fibre in my area, but every night from 5 onwards my connection speed drops from the normal between 80 and 120 mbps to between 1 and 3 mbps, logged numerous calls, messages but still no resolution. The last I was told that it was a MTN problem, and a call was logged with them. I am not getting this service for free, why am I not getting what I am paying for?? I understand the fair usage policy, but this is ridiculous.