Your internet provider has nothing to do with your 5gHz band, that is something YOU do on the router itself.
Anyway, the issue is that most routers broadcast in 2 frequencies: 2.4ghz and 5ghz. Lots of people tell their routers to name both frequencies the exact same name and then let your device decide which one to use based on the signal strength (for example, inside the house, my phone might connect to the faster 5ghz, and in the backyard where the 5ghz doesn’t reach, it will just switch to the 2.4ghz.
The problem is that most iot devices (smart home devices, not just Wyze, but most of them) only support the 2.4ghz band for all sorts of reasons including to make sure the signal can be reached, avoid costs of dual support, save space from dual support to make the device a little smaller, 2.4ghz is almost always available and supported everywhere, whereas 5ghz sometimes isn’t reachable, and many other things. So, when you try to set up an iot device that only has 2.4ghz on a router that is broadcasting both signals using the same name and identifying info, it sometimes confuses the devices and they might report back that the signal name you are trying to use is the wrong frequency. Most people resolve this by setting up a separate 2.4ghz SSID on the router solely for iot devices, so they have their own name, and connection and everything that has no interference or confusion.
If you don’t know how or can’t figure out how to set up a separate SSID broadcast like that, and plan to keep your 5ghz and your 2.4ghz the same name and use the iot devices on that same named ssid, then all Wyze is saying is that sometimes it helps to temporarily disable the 5ghz band in your router while you set up your devices (this just makes your life easier sometimes). Once set up is complete, go ahead and turn everything back on, and you should be fine. I would still strongly recommend giving them their own SSID name to connect to on those routers, but if that’s too hard to figure out, don’t worry about it. Most people are able to get it working fine without any of the jumping through hoops I just explained. I am only telling you all those details because you asked for an explanation. If you have problems I’m sure it can be figured out one way or another. Lots of people use mesh networks, including this one and are fine using them.
Still, you don’t have to talk to your ISP at all, it has nothing to do with them.
I hope that helps. Best wishes with your exciting new Mesh WiFi that should make things significantly better for you in general!