How do I get service on my iwatch?

I believe it’s T-Mobile digits I paired the watch and phone but the watch cellular data wont turn on. It says it’s connected to T-Mobile cellular is on cell data as well but status says no connection. I messaged T-Mobile 3X already and told me they fixed it. I have to leave without my phone to really know if I can receive or make calls/msg. And yes it’s a gps cell ultra iwatch. Any help?