Native Mobile VoIP Calling Platform Development (iOS, Android, Backend & Admin Panel)

Native Mobile VoIP Calling Platform Development (iOS, Android, Backend & Admin Panel) We are looking for a highly experienced development team or senior engineers with proven commercial VoIP and telecom experience to design, develop, and deploy a premium international prepaid calling platform. This is not a standard mobile application. It is a telecom platform requiring expertise in SIP, carrier integration, real-time billing, payment systems, and scalable backend architecture. Project Scope The project includes: - Native iOS application (Swift, CallKit, PushKit) - Native Android application (Kotlin, Telecom API, ConnectionService) - High-performance backend platform - Real-time prepaid billing and wallet system - Subscription and minute package management - Multi-currency support - Multiple payment integrations (Mobile Money, Credit/Debit Cards, PayPal, Apple In-App Purchase, Google Play Billing) - Callback functionality for low-connectivity environments - Comprehensive web-based admin panel - Secure REST APIs - Production deployment - Complete source code, documentation, and full intellectual property ownership Required Technical Experience Applicants must have proven experience with: - SIP, RTP, SRTP, STUN, TURN, ICE, and NAT traversal - FreeSWITCH, Kamailio, OpenSIPS, or Asterisk - Carrier and SIP trunk integration - CallKit and PushKit (iOS) - Android Telecom API and ConnectionService - Background VoIP calling and device optimization - Real-time prepaid billing or rating engines - CDR processing and reconciliation - Payment gateway integrations - Multi-currency wallet systems - Secure, scalable backend architecture - Cloud deployment (AWS, Google Cloud, or Azure) Proposal Requirements Please include the following: 1. Links to live VoIP or international calling applications you have built. 2. Your exact role in each project. 3. Your team's technical expertise and structure. 4. The technologies and architecture you recommend for this project. 5. Estimated development timeline. 6. Estimated budget. 7. Confirmation that all source code, documentation, and intellectual property will be transferred upon project completion. Important Only apply if you have demonstrable experience building commercial VoIP, telecom, or international calling platforms. Generic mobile app development experience alone is not sufficient. Applications without relevant VoIP or telecom experience will not be considered. We are looking for a long-term technical partner capable of delivering a secure, scalable, and production-ready telecom platform built to enterprise standards.