Issues with Voip on openvpn

NethServer Version: your_version
Module: your_module
I use nethserver 7 and I have an issue with VoIP over openvpn. I have a small network with a functional outgoing PBX connected to the nethserver. The PBX has a trunk line to a service provider connected to it directly. I then needed to make calls from home due to the corona virus lockdown but the problem is that after setting up openvpn in a routed mode, I can connect to the PBX on which is my network up given by the dhcp on my nethserver. I use zoiper software phone and it registers immediately and I can make calls but the issue is that I can hear the voice of the person I called but the person cannot hear me, but if I am in the office, I can make good calls without issues. It is clear that there is an issue with the VPN connection. Please help.

Would you please provide a bit more information about your subnet setup? Which subnet is Green, which is the ip address of your PBX and which subnet is you OpenVPN?
Did you provided bandwidth settings for your RED connection?
Is QoS configured for traffic from OpenVPN to your PBX?

Thanks to everyone that showed concern. I have been able to resolve it based on the subnet issues that Mr Michael Kicks raised. Thank. Lastly I want to ask, how many users can I create on nethserver and how free is openvpn. I have read their licensing stuff but I need to know if I can use it as it is for 50 users

Good day everyone. I need your help. I hope all you guys are safe and protected from the pandemic out there. Love you all and please take all safety procedures seriously.

Still on this nethserver VoIP issue. I want to paint the true picture of my installation. We have a nethserver installed and it has two wan interfaces. Before the introduction of the nethserver, we have a mikrotik router that was used to configure firewall rules and content filter rules for the local internal network. And our PBX server which is a dlink dvx 9000 was connected to the mikrotik for us to use the sip service from a provider. We have another provider whose link connects directly to the e1 port on the PBX. That one is working fine. Now we want to remove the mikrotik and use the nethserver as the route for the sip service route. On the mikrotik, we have a policy based routing, NAT rules and some configuration. How do I translate that to nethserver? Please help