Pathetic support and dramatic decline in network speed in Richmond/Melville

I have signed up with Rain 5G in Melville/Richmond when full lockdown started as they promised the fastest WiFi connection in the area. For a while it went well. However, over the last couple of months, I have been experiencing dramatic drops in network speeds, (and often complete drop temporary drop in connectivity) especially in the afternoons. As an academic who needs to deliver classes online, this has caused multiple disruptions recently in the online classes I had to deliver, and often in a cancellation or postponement of the classes (which is extremely disruptive to the students and my own schedules). Worst is, today I have been on the on hold on telephone for 20 minutes, and nobody answered the support line. The website does not provide any e-mail address where I can log a complaint. The support tab only takes you in circles which do not help me at all.