I have opened port 3389 RDP on my router so that I can access my work computer from home. However, I'm not yet able to RDP my work computer from home since there is a proxy server through which all Internet traffic passes. When I do a port scan, port 3389 is open on the router but not on the proxy server. I have requested my ISP to open the port on the proxy server but he tells me that he is already using port 3389 for VoIP. What can I do? Please help.