By default, you will receive a pop-up notification for all incoming calls. However, it's possible that the default settings have been changed. Please follow these steps to re-enable call notifications:
- Go to Settings > Apps & notifications > Notifications.
- Scroll down to locate the "Phone" icon. Make sure the toggle to the right is ON (toggled to the right).
- Once confirmed, tap the "Phone" line item, then tap "Incoming calls"
- Tap "Behavior" and select "Make sound and pop up screen"
- Test it out by having someone call your phone. If needed, please reboot your device.