I’m also getting the exact same issue with the exact same phone, iPhone 15 pro max, Verizon Carrier in Stratford/Trumbull, CT. Went to use my phone for contacting work and the call got cut off-- thought it was a signal pocket, but my phone would only show SOS. I also tried airplane mode, full reboot, switching on and off. Nothing fixed it. I called Verizon customer service and got automated bots that were not helpful and a text telling me directions to reset my phone which I have only had for 2-weeks. I had a meeting, so I left the issue and after it ended, I noticed that suddenly my phone has signal again. Reading all of these similar concerns, I am very anxious about having this phone as a reliable communication mechanism. I have timely, legally bound work that needs to be completed and my phone is often my connection. Highly concerned. I hope that Apple will work on this with Verizon to make adjustments for those of us who have made this investment.