I am able to select which fxo port to send the outbound calls. Now all the calls from all fxo ports go to a fixed extensions. When I am trying to route different fxo ports to extensions, it fails.
The way of freepbx's thinking is defferent from Asterisk-GUI. In freepbx, it requires DID/CID for routing. The fxo DID is defined in Zap channel DID.
It is wasting of our time in exploring non-mature GUI: FreePBX.