Hello,
By default, the firewall on the RUTX50 does not allow forwarding traffic from WAN to LAN, even when NAT is disabled. In your case, you will need to add the LAN zone to allow forwarding from the WAN zone in the WAN zone settings:
If the Callbox still cannot reach the RUTX50 LAN network, could you please share a simple sketch of your network topology, including the IP addresses?
Additionally, there was a similar topic regarding accessing the LAN network from WAN that might be helpful or provide some insights for your setup:
Best regards,