React Native VoIP Call Notification via FCM/APN

I need a React-Native expert to troubleshoot and implement the code for incoming call notifications using FCM/APN on Android/iOS devices. My existing set up for receiving VoIP video calls is working well, but the incoming call notifications are not being received.

Key Requirements:
- Modify and implement the React-Native code to handle incoming call notifications
- Test the feature on Android/iPhone test devices, as it does not work on the simulator/emulator
- Communicate and coordinate with me during the testing and implementation process

Skills and Experience:
- Strong proficiency in React-Native
- Prior experience with VoIP and video call integrations
- Expertise in Android/iPhone app development
- Familiarity with FCM/APN and call notifications coding

You can find the references to the code I am currently using here:
- https://github.com/react-native-webrtc/react-native-callkeep
- https://github.com/bharathselva28/react-native-incoming-call-android

Please note that no styling is required, just the code implementation.