Assuming there is a straight forward setup at each end, you either have a routing, firewall, NAT, DNS or application (phone system) issue. You've stated that both sides can access each other's resources, so the networking should be in place, but I hate to assume, so we need more details:
Post a network map, so we have a better idea of how things are connected.
Post the server1.conf from server and the client1.conf from the client.
Post a screen shot of the firewall rules from the LAN tab and OpenVPN tab on each end
What kind of phone system is being used and what is it running on?
Are there any blocks in the logs at either end?