Hello Sir,
According to your project details, video call integration of maximum four participants including caller is one of your requirement.
I have recently completed a project based on WebRTC video call android application. The deal with my client is in the final phase,
he has already created milestone and in few days you will see review of the same on my profile.
The application is created using a free tier EC2 instance of amazon web service's server, it will be free for 1 year. Application
is also dependent on the firebase for OTP login and user data storage, the data is just token id and mobile no of user. So firebase will charge nothing until we reach some thousands of users. In case if you don't know about WebRTC technology, so let me tell you that it's a open source technology by Google, hence it's totally free.
I can modify the source according to your requirement. Please initiate chat so that we can further discuss about it.
Regards
Nitin