Shooting in the dark here, i went here:
http://www.vonage.com/help.php?lid=nav_help
I looked at one of the install deal and try going to 192.168.15.1 and type in router for the username and just click login.
If you are able to login, you might want to change the password asap for security reasons and then look if you can port forward from there.
tell us what hardware you got, which one?
personally i signed up here:
http://www.dyndns.com/
I went to Dynamic DNS, put my ip in there (real not network), chose an "Address" and there i go. I put that address in serverlist.cs
edit: you open razor, on server, they would put your name.whatever.whatever you choose on dyndns, port 2593. Make sure that "patch client encryption" is checked but OSI is not checked. and click connect, it will open the UO client for you and you can log on.