Twilio developer evangelist here.
If you read through the documentation on how Proxy manages numbers you will see that at one stage during the natural assignment of numbers you may end up with two participants in a session using different numbers to talk to each other.
You want this to be the default behaviour though.
I'm not sure there is a setting within Proxy that uses this selection technique. The only way you can impact the number selection is by choosing "Prefer sticky" (prefer to choose the same number for sessions) or "Avoid sticky" (prefer choosing a different number for each session) and these options still don't fit your requirement.
There is one other option. Use Proxy, but handle the number selection yourself.
When you create a participant for a session you can provide a ProxyIdentifier
which is the proxy number you wish for them to use in the session. If you create your two participants with different ProxyIdentifier
s then you will get the behaviour you want. The only drawback is that you have to control the number selection behaviour, rather than Proxy doing so.
Let me know if this helps at all.