Phone Disabled

My phone has been acting up since I got it when the XR was fairly new. Today my phone wouldn't let me type when I was in my messages. When I tried to exit the app it would not let me. Then I tried to open it again and It kept on crashing as soon as I opened it. I tried with all different apps on my phone. Some of them would stay up but where frozen. I opened my photos and when I clicked on one and I tried to go back to view the others it would not let me. So I decided to close all the apps and just let my phone sit. About 5 minutes later I tried again but nothing would work so I tried to shut down my phone and restart it. When I turned it back one it instantly popped up iPhone is disabled connect to iTunes. I don't have wifi and I tried to use my moms data because my phone won't let me connect to wifi or turn up or down the brightness nothing. my computer is taking forever to sign me into iTunes. I have a fit bit that is connected to my messages and if someone texts me my phone vibrates like I got a test message and my Fitbit shows the message but I have no way of accessing it on my phone! I'm not sure what is wrong with it or how to fix it. Someone at my work said sometimes when you get an iPhone that is brand new you can get faulty ones and you need to turn it in to get a new one. Is that true? Any idea on how to fix this?