Tried hard but can't deliver stable fibre

I posted a couple of weeks back about my continuing 'terrible fibre delivery' by two companies - Home Connect as my service provider, and Vumatel as the network provider. I pointed out that I pay for 200MB/s up and down, pay them on time every month, but have a wildly fluctuating fibre delivery. Both companies took notice, arrived at my house, changed their 'boxes' - routers etc, and things have now got worse. It is quite dismal to watch the Springboks against Argentina, and continually see on my TV 'unstable connection'. Home connect insist they have done everything and have walked away. Vumatel's engineers didn't even know what the black box they replaced actually did. So much for hi-tech service providers. Home connect suggest that I should install a mech system, which I will, but when my TV is next to their router, and I work with my computer 3 meters away from their router (and the same problem with my phone) and when 5G on my phone is faster, which I continually have to change to to upload, large files then asking me to install a mesh system (for the rest of the house) is a bit feeble. As I keep pointing out, fibre shouldn't fluctuate depending on the usage in the area, but when Sasha Feinberg Ngomazulu is about to break Percy Montgomery's record of 35 points in a game, and my TV freezes - well time to look at Telkom maybe? Just saying.