Hello pragnyaallu,
Thank you for using Apple Support Communities. It's our understanding that your iPhone screen isn't responding as expected during phone calls. We're happy to help.
If you haven't already, try restarting your iPhone. This step can resolve many unexpected behaviors. Restart your iPhone
Also, make sure that your iPhone has the latest software.
Update your iPhone, iPad, or iPod touch
If the issue persists, remove any case or screen protector and test the issue again. Let us know the results. Please include any other troubleshooting steps that you may have tried.
Have a great day!