Iphone 8 Sim won't work

I was on online chats for 7 hours today, trying to get the SIM in my iphone 8 to work. What a nightmare. To waste an entire day is inexcusable. All I got was the run around. Agents dropped me as soon as they could. Now the phone doesn't work at all so I have no phone. I hope I don't have an emergency. A car crash. Anything that requires my phone. Multiple chat sessions were pointless. I'm beyond angry. Once my contract is up, I'm out.