Hello

My phone has recently been disconnecting from the network leaving me with no internet connection nor the ability to make and receive phone calls. When I go to make a phone call, it will say the phone is in flight mode and needs to be turned off. I turn it off but when I go back to check, it checks the flight mode back on. This seems to be happening at night but I'm not sure how relevant it is to the actual problem. Should I do a system reset? Sometimes I'll restart my phone and it will be normal for about 15 minutes but then the network 4g symbol will turn from green to white, and then the no network symbol will show in the status bar. I don't know what to do, please help. Thank you.