Ok ok… Other versions might not work but 6.2 does! Here a screen… I tried it with my brother and it worked for us
P.S He used 8.5… I’ve used 6.2
cool, what you make
If your brother is on the same network as you, then I’m not surprised. Voice calls are only a problem when it comes to situations outside of LAN networks. 
Nope… I’ve called him from 8.5, 7.0 too but it didn’t work… With 6.2 it worked
Call your friend and come back
What are the ports you need to forward for this to work? 
5004