incoming call are not showing on the screen for iphone 10 but phone is ringing

This is definitely not expected behavior, but it seems to be a software issue. I would try the following steps first:

1. Check for a Carrier Settings Update - Update your carrier settings on your iPhone or iPad
2. Try powering your iPhone X off, then back on - Restart your iPhone, iPad, or iPod touch
3. Try force restarting your device

   On an iPhone X, iPhone 8, or iPhone 8 Plus: Press and quickly release the Volume Up button. Press and quickly release the Volume Down button. Then, press and hold the Side button until you see the Apple logo.

4. Try resetting your network settings
   • Settings > General > Reset > Reset Network Settings.
   • This also resets Wi-Fi networks and passwords, cellular settings, and VPN and APN settings you’ve used before.

If the issue persists, try the following (which is more time-consuming):

1. Create a backup of your iPhone using iCloud or iTunes - How to back up your iPhone, iPad, and iPod touch
2. Erase your iPhone - How to erase your iPhone, iPad, or iPod touch
3. Set up your iPhone as new (do NOT restore from the iCloud or iTunes backup just yet)
4. Place a test call to your iPhone X from another phone and see if the issue is resolved
5. If resolved, follow steps 2 and 3 again, but restore from your backup this time
6. If the issue returns once you restore from the backup, there may be an issue with your backup itself and you may need to set up the phone as new and start fresh to resolve the issue

I hope this information helps resolve your issue.