Phone keeps saying no service even though I have updated it

I have an iPhone 7 and I keep having problems with my cellular claiming that I have no service. I few months ago I went to Verizon and asked what was wrong. They told me that I needed to update it and that had been working for a bit. Then it stopped working. I have everything up to date and it still wouldn’t let me make any call or texts. I reset the entire phone. I deleted everything from it (like they told me at Verizon) and then restored my old info back onto it. It worked momentarily but then it went back to no service. What do I do?