Flutter Call Notifications Fix

I'm facing an issue with my Flutter application where call notifications are not appearing while the app is in the background, but they do show up when the app is in the call screen. This issue occurs on both Android and iOS platforms.

Key Requirements:
- Experience in Flutter development
- Expertise in handling notifications on Android and iOS
- Ability to debug and fix issues related to call notifications in Flutter apps
- Understanding of app behavior in background vs foreground