I need a production-ready softphone for both iOS and Android built on WebRTC and standard SIP. The app will authenticate users with a simple username-and-password flow against our existing PBX or have an onboarding process for new customer, then expose a clean, corporate-style interface that matches the rest of our product line. Core scope • Implement voice calling with transfer, local audio mixing for two-party and ad-hoc conference/merge, BLF, hold/resume and DTMF. • Add visual voicemail with message playback, delete and download. • Enable two-way SMS inside a conversation view. • Web browser view to show our webpage • Contact lists (local & hosted) • Recent call history Technical notes – WebRTC should handle media; SIP (UDP and TLS) drives signalling. – Push notifications are required for inbound calls and messages on both platforms (APNs & FCM). – Call quality stats (MOS, jitter, packet loss) must be surfaced for troubleshooting. – The UI should feel polished, professional and brand-consistent; think clear typography, restrained colour palette, unobtrusive icons. Deliverables 1. Native builds for iOS (Swift/SwiftUI preferred) and Android (Kotlin/Jetpack Compose) ready for TestFlight/Internal testing using React Native/Flutter or similar. 2. Complete, well-commented source code in a private repo. 3. Configuration guide showing where to plug in SIP domains, stun/turn, push keys, brand assets. 4. Quick start QA checklist demonstrating successful registration, call flow, voicemail retrieval and SMS send/receive. Acceptance will be based on successful lab tests against our Hosted PBX instance and a short live demo using two concurrent handsets.