SMS Integration for Multi-Platform App

I'm looking for an experienced developer to implement an SMS feature in my app, which is built on both iOS and Android platforms. The SMS functionality will be used for user notifications, two-factor authentication, and marketing messages.

Key Requirements:
- Integrate Geezesms as the SMS service provider
- Implement SMS features for:
- User notifications
- Two-factor authentication
- Marketing messages
- Ensure smooth functionality on both iOS and Android platforms

Ideal Skills & Experience:
- Proficiency in mobile app development for both iOS and Android
- Experience with SMS integration, particularly with Geezesms
- Strong understanding of security protocols for two-factor authentication
- Background in implementing notification systems and marketing message delivery

Please provide examples of similar work done and your approach to this integration.