Ringless Voicemail Architecture using Python

I need an Telecomunication Engineer. I'm looking for a tech who already has completed a Ringless Voicemail drop system. We are US based company and will target users in US only so will calling 10-digit US phone numbers. We would ideally prefer some open source technologies to be used with it like FreeSwitch etc.. If you Already have completed a ringless voicemail drop system please bid. Please include the past project info. Preferably developed using python.