Poor Service

Fibre has recently been rolled out in my area and installed in my house. Initially I was happy with Home-Connect however after a few days my download speed drops to below 10Mbps, sometimes even as low as 2-3Mbps, after 5pm. I pay for a symmetrical 100Mbps line. What is going on??? I know for a fact that my fibre line is working perfectly because my upload speeds hardly drop below 90Mbps. I emailed Home-Connect repeatedly and I get no response. What kind of customer service is this? This is very poor from you, Home-Connect! I would not recommend Home-Connect as an ISP.

I'm getting those kinds of speed drops even when no other device is connected to the network.