Hi and welcome to the forum
Can you please clarify what self help troubleshooting tips you've tried.
The generic ones are ->
On the iPhone hold down the Sleep/Wake Button and Home button together until the Apple Logo shows. Then On seeing this Apple Logo release both buttons ,and the iPhone will reset , which has been known to clear most glitches.
Settings -> General -> Reset -> Reset Network Settings.
Forget the network in WiFi Settings.
Restore the iPhone via iTunes (Make a backup to iCloud and or iTunes first)
Are you jail broken ?
If you have a local Store then let a Genius Bar Employee run a diagnostic via an appointment through
https://www.apple.com/uk/retail/geniusbar/What iOS are you currently on ?
Good luck.
😎
Current Phone >
Samsung Galaxy s²³ Ultra 512gb Phantom Black.