Hi Ajay_Rajawat,
Welcome to the Apple Community,
where some of us do our best to help each other troubleshoot.
Apple support have an article online that may help with your network issues:
Check VPN (Virtual Private Network) and third-party software to help resolve network connectivity issues
https://support.apple.com/en-us/HT211905
Wondering which iOS you have installed on your iPhone,
and
which app(s) you are using when the screen hangs.
.
iOS 15 overview
https://www.apple.com/ios/ios-15/
If your iPhone has frozen:
https://support.apple.com/en-au/HT201412
Hope this helps you :)