Please help me WebAfrica - speeds are terrible on 100 Mbps / 100 GB line.

I've been a customer of WebAfrica for 3 years on the 100 Mbps line but I would estimate I get those speeds probably less than 20% of the time. I am also on a capped line (100GB) so there should be no issues. This weekend as an example I've had speeds of about 2 Mbps and this is sitting right next to the router which is a decent router (Tenda). What can be done, not once has a technician come out to my house to sort this out and they have reset my line virtually, and then all of a sudden it is super fast again...I need to get as close to 100 Mbps the majority of the time otherwise I'm paying for a service that is not being delivered. Please help me WebAfrica? Thank you,