There is a Free Open source video conference app in mobile and web that is Jitsi
Why I mention Jitsi?
In your apps you can create easily special rooms or conference pages with jitsi links.
Because in jitsi it is free and you can join a conference directly with a link. For example,
Jitsi video conference room tempalate is: http://meet.jit.si/
if you add anything to this link , you can get a conference room
In your app Bahadir can send a conference request to Peter for example. you can use glide data template and create uniqe links
So room is ready. I think very usable and free