Cross-platform Social Networking App Developer

I'm seeking a talented mobile application developer to create a social networking app for both iOS and Android. The app should be engaging, user-friendly and packed with key social features.

Key components of the app:
- User profiles: The app should allow users to create and customize their own profiles.
- Messaging: An in-built messaging system is a must. This should be intuitive and easy to use.
- Integration with third-party calling software: The app should seamlessly integrate with popular calling platforms.
- Chat service: Beyond one-on-one messaging, there should be a robust chat service for group conversations.
- Payment gateway integration: To support in-app purchases or peer-to-peer transactions, reliable payment gateway integration is necessary.

Ideal candidates for this project should have:
- Proven experience in mobile app development, specifically for social networking platforms.
- Expertise in both iOS and Android development.
- Prior experience with messaging systems and third-party software integration.

Please include your portfolio of similar projects in your proposal. I'm eager to see your creativity and technical skills in action.