iPhone XR no network error

Ok so I have a iPhone XR (2. Of them) purchased from T-Mobile, they’re both paid for (1500.00) in cash, so I own them, I’ve been using simple mobile sims in both phones for almost 2 months. They worked fine. All of a sudden on New Year’s Eve I lost service in both phones and it hasn’t returned. I’ve done ask the troubleshooting methods even factor reset my phone. My sim is active and works in other phones. No sim works in my phone at all, including T-Mobile sims. Plz help