Lets Summarize the app:
1) Makes VPN calls.
2) Send Messages.
3) Send Chats(conference, private and group), It should be, message, voice and/or video.
4) Calls should also be video and voice features.
5) Major Admin can create, activate and deactivate Sub Admins.
All Admins can monitor realtime location of users.
Admins should know numbers of users and have access control also.
6) Users should be identifiable ( Should fill a form before joining and assigned a number automatically or manually by admin).
7) Conference call feature should be available.
8) Conference chat and group chat features also.
Major Admin should determine how many numbers can form a group (can be unlimited,) and only him can create groups then all Admins can assign members.
Individuals cannot join a group but can only be added by an admin.
App should be customizable by Major Admin. i.e. logo, footer, copyright section, colors, etc...
Please discuss more details about duration and budget with private chatting.