cellular data is not available during this call

Hi there Saud_6,

Welcome to Apple Support Communities. We suggest resetting the network settings to help with this trouble. Follow these steps to do so:

Reset your network settings. Go to Settings > General > Transfer or Reset iPhone > Reset > Reset Network Settings. This will erase all current saved settings, including Wi-Fi passwords, preferred networks, and VPN settings.

Further troubleshooting steps can be found in the Apple Support article:

If you can't make or receive calls on your iPhone - Apple Support

Feel free to reach back out if you have any questions.

Best regards!