Callgram has enhanced the mentioned app with a service fully integrated with your contacts and phone numbers. You can call to your Callgram counterparts, and leave a message if they are absent. They will be able to listen the voicemail messages. It has own features:
- Free calls.
- SIP autoprovisioning.
- VoIP solution.
But Callgram also inherits all the features that the mentioned system has:
- Send an unlimited amount of messages, photos, videos and files of any type (.doc, .zip, .pdf, etc.).
- Very fast
- Cloud storage.
- Group chat.
- 100% Free
The only difference is that we have included ads inside the app in order to maintain our VoIP servers. We are sorry about it, but it has been the most transparent way to provide this VoIP service for the end users.
This app is open source.