How to block hotspot tethering to public wifi?

We recently upgraded our internet to 200mbps fiber and still getting complaints from some people that the speeds are slow.  Upon researching it looks like numerous people instead of using their devices as hotspots using their own data, they are tethering their device off our wifi (not a direct connect to our wifi) creating a router from what I can gather from my research.  Is there a way to block people from tethering their device?  We have a specific guest network they can connect to which will automatically disconnect them after 12 hours, but this connection many people are using is different.  In fact, when I look on my phone for available wireless networks I can see 9 additional aside from our 4 corporate SSID's (3 are password protected and 1 is for guests).  With people doing this, it's affecting the speed for people who are trying to conduct meetings or video calls with a wifi connection to our guest network.  Can we block these people?