Cross-Platform Communication App Development

I'm seeking an experienced mobile app developer (or team) to build a cross-platform mobile application for iOS and Android that supports real-time communication features, including voice calls, video calls, and instant messaging/chat. I already have a working SDK that provides the necessary backend and media handling; your task will be to design the UI/UX, integrate the SDK features, and ensure the app is fully functional and optimized for performance.

The app should include:
- User registration/login (email/password and social media logins: Facebook, Google, Twitter)
- One-on-one chat, voice, and video call features
- Push notifications
- Modern, clean, and responsive UI design
- Integration of the provided SDK for communication
- Testing and deployment-ready builds for App Store and Google Play

Ideal Skills and Experience:
- Proficiency in mobile app development for both iOS and Android
- Strong UI/UX design skills, with a professional aesthetic
- Experience integrating third-party SDKs
- Knowledge of implementing social media authentication
- Familiarity with app testing and deployment processes

Please provide examples of similar work done. Looking forward to your proposals!