I need a mobile PBX application that lets my team place and receive internal calls entirely over our local Wi-Fi network. The app must run smoothly on both iOS and Android and register 51-200 extensions without relying on cellular voice or external trunks. Core functions I must see on day one: • Call forwarding, including unconditional, busy, and no-answer rules • Visual voicemail that stores messages locally and syncs with the PBX I have no immediate need for call recording, yet I prefer a codebase that leaves room to add it later. Whether you build the PBX side (Asterisk, FreePBX, 3CX, etc.) from scratch or integrate with an existing server, the result has to deliver reliable SIP registration, push notifications for incoming calls, TLS/SRTP security, and a clean user interface branded for our company. Deliverables • iOS and Android apps submitted to TestFlight / internal APK for testing • PBX configuration files or clearly documented steps to connect to our current server • Source code with build instructions, including any third-party libraries • A short hand-off call walking through user on-boarding and admin management The project is complete when I can install the app on multiple devices, see every extension online, forward calls, and pick up voicemails without leaving the office Wi-Fi. If this matches your expertise in SIP, push call handling, and cross-platform mobile frameworks, let’s talk timelines and milestones.