Service isn’t working

I have an iPhone 7 and I’ve tried almost everything I could. My phone is up to date, but it says that my service won’t work until I update my phone. A carrier update won’t pop up when I go to settings, I’ve restarted my phone, I’ve put it on airplane mode for a few seconds, I took out my sims card, and etc. It hasn’t been working for 3 days now, but I can still text when on Wi-Fi. My carrier settings won’t even load and is blank. What should I do?