They are having issues with T-Mobile internet not cell service.
T-Mobile internet is heavily dependent on wireless 5g signal at your home (5g cell, not 5g internet
). Performance issues will be in one of two areas (or both):
1. Poor wireless signal from T-Mobile gateway to T-modem (cell signal)
2. Poor wireless signal from T-Mobile gateway to end devices (wifi signal)
Connect a computer directly to the T-Mobile gateway (ethernet jack), then go to a site called fast.com and see what your speed is. This eliminates the wifi side. If speed is poor (less than 50mbps) then try moving your modem around to see if you can improve it. It may just be location of the modem.
If you have a concrete home it will not work as well as a stick home - concrete tends to kill cell signal no matter who you are using. In this case the best location for the gateway is on a sill of a window.
If speed looks good when connected directly, disconnect and test speed via wifi. When the computer is close to the gateway, speed should be fairly close or equal to direct connect.