Windows Softphone: Conferencing, Recording, Voicemail, messaging

I need a purpose-built softphone that runs natively on Windows 10/11. Beyond routine SIP calling, it must deliver three core capabilities: reliable call conferencing, built-in call recording (local file storage in a common format), and an intuitive voicemail system with message notifications... (Budget: ₹12500 - ₹37500 INR, Jobs: Android, Asterisk PBX, Audio Processing, C# Programming, Mobile App Development, SIP, Software Architecture, Software Development, User Interface / IA, VoIP)