New user, is it still possible to separate 2.4 and 5g networks?

@hanly2 yes you can. I have both 5Ghz and 2.4Ghz as some of my devices like cameras and Google Nest thermostats use 2.4. 

https://www.t-mobile.com/support/public-files/attachments/T-Mobile%20High-Speed%20Internet%20Gateway%20End%20User%20Guide.pdf

The link takes you to the old gateway but much of the setup information is the same. You should use your T-

Mobile Internet app. Once logged in, at the bottom of the screen tap the Network tab. Then tap the + in the lower right corner and add your both your 2.4 and 5 Ghz networks from the gateway. Use the original information you used to setup the gateway.

Good luck!