Modem issues?

Hey, I could really use some advice here. So, I’m currently on a basic plan with Xfinity and using their wired modem. I’m looking to make the switch over to wireless, but I was wondering if I could just go out and buy my own modem instead of paying that monthly rental fee to them every single month. Ideally, I’d love to pick up something universal—you know, a modem I can just take with me regardless of which provider I use down the road. When I asked about it, they told me it wasn't really an option because most providers prefer you to use their specific hardware, but I'm thinking maybe they're just wrong? Is it actually true that one modem can work just as well across different service providers, or is there some catch I'm missing? I guess I just want to save a few bucks if possible.

thanks!

So, I was thinking about grabbing my own router. People keep telling me that a modem and a router aren't actually the same thing, and they say I could just pick up some universal router that works regardless of which ISP I'm using or what kind of modem I have. If my internet connection itself is solid, is doing this actually a good move? Or is it one of those "quick fix" solutions that ends up being a total headache later on...

I'd love some advice here

Thanks guys

Maybe grab something like this wireless router that features a dedicated WAN port.