I have configured a 3CX Free Edition Phone Server on Windows 2003 with all the correct ports forwarded, but an incoming or out going call on my SIP provider Blueface Ireland can only hear me and I cannot hear them. Just to make sure the NAT was not the problem I put the server in the DMZ and still no luck. I am beginning to think the router is at fault as it is only a pretty cheap TP-Link Wireless one. Windows firewall is also off. Just wanted to check if anyone knew a solution to this problem.