I've had iPhones and been with Verizon for over 20 Years. No previous major problems. Big advocate of both.
I now have the iphone15. Worst phone ever, worst service ever. People call: it goes straight to voice mail, yet it doesn't show I got a call or a voicemail. People call: they get a busy sound. People call: they say it rings forever but i have no indication. People call: drops calls over and over. I call out: call failed. Move around: call drops. All this is random! Might be 1 time a day or many more. Internet service, apps and texting are fine. I have 8 pages of notes speaking with Verizon. Many, many, many hours. Nothing works. Most phone calls promised are not returned.