For the time allotted (based on your budget) I would recommend some off the shelf open source packages, with a common/shared platform for inter-package communication.
Relevant Skills and Experience
Long time FreeSWITCH user and developer, previously worked directly for FreeSWITCH Solutions. Long time OpenSER (and derivatives: OpenSIPS,, etc.) user and developer. 100% carrier experience.
Proposed Milestones
$1250 SGD - Project as defined or re-defined in conference call.
Additional Services Offered
$1 SGD - On-Going maintenance and monitoring through 373K.