How to change from TMobile to 5G carrier?

Hi! It says that you’re using iPhone 4S. This iPhone only supports up to 3G connections, meaning that iPhone 4S cannot be used with 5G SIM plans. You will have to buy a newer iPhone to access 5G: iPhone - Apple

Have a great day!

See this list and choose your preferred carrier, after contacting them:--> Wireless carrier support and features for iPhone in the United States and Canada - Apple Support

Regards

Giulio