Call Button - Cancel - Virus

My iPhone 11 got a pop-up that states to call a phone number. I pressed cancel, but it kept popping up, and I think it overwhelmed my browser. I closed it, but as soon as I tapped the app icon, the same pop-up appeared before seeing the page. I closed it again, and my phone started acting funny. I couldn't open anything, close anything, I couldn't even restart my phone no matter how long I held the volume up and power button. My phone is at 30%, so I managed to turn the brightness up, and when it dies, I'm going to turn it back on and hope for the best. - - In short, I know it is a scam, but I can't shut down / turn off my iPhone to make it go away - I also can't access anything on my iPhone. Please help. I don't know what to do.