Tringy

which allows to create full-featured, customizable and white label mobile communication applications to offer end-to-end mobile VoIP communication services such as voice, video and text. Tringy is specifically designed for small and medium VoIP providers and retail operators who wanted to leverage the OTT based Mobile VoIP Communication trend to expand their service offerings, grow into new markets and achieve higher revenues.

Features:

Call landlines and mobiles for extremely low-rates around the world
Free app-to-app audio/video calling, instant messaging and media sharing
Subscribe to various packages, recharge and transfer mobile VoIP balance
Send/receive money, pay utility bills, top-up mobile balance internationally and many more
Highly configurable and secure with TLS, SRTP protocols
Compatible with SIP Standard IGW