internet

I’m not sure what you mean, but you ‘can’ keep an existing company (e.g. Spectrum, Xfinity) and T-Mobile Home internet.  Personally I currently have both.  At some point, I’ll cut the cord with Spectrum, as T-Mobile Home internet ‘for me’ has been quite good, and much lower cost than Spectrum.

If you have your own WiFi router, you may have to unplug one and plug into the other ‘if’ you want to reuse your WiFi router and its services.