VoIP Software Developer with SIP & RTP Expertise

I'm in need of a skilled software developer experienced with SIP and RTP protocols for our VoIP application 3cx. This application will primarily focus on facilitating calls directly out of a 3CX server to a phonenr. A second line needs to be setup out of server towards the 3cx app. If the the first line connects the secondline should take over the first line. Key requirements: - Expertise in SIP & RTP protocols - Proven experience in developing VoIP applications - Skills in Linux OS software development - Familiarity with 3CX server operations and API , IS A MUST If you can create a seamless, efficient solution, I would love to hear from you.