Throttling of Download Speeds

I am trying to figure out what the 5G Sales Pitch and the Home Premium Cost of R999 Monthly is about. I initially got Speeds of between 30 - 50 mbps. When I downloaded Videos for Offline Viewing it used to download at between 1 - 2 mbps. This I could live with. I have now installed the Device Outside as windy days would affect my internet connectivity. Daily speed checks show that I get over 100 mbps. Now my downloads speeds do not exceed 80kbps. Ranging from 40 - 80kpbs. This is very very frustrating. Its not just at a certain times of day, its all the time.

Now why would Rain be throttling my download speeds? and what am I paying for? I in no way have I even exceeded any Fair Use limits. This seems to be just for video downloads. Other downloads seem fine including streaming.