Hi! My boss sent me a Cisco IP Phone 7960 so I can work remotely. I plugged it into my router... I can make it ring and it can ring out but no voice can be heard and it lacks dial tone. I took some time to set Inbound Filter Rules to open up these ports to their US IP adresses, but still no go. What am I doing wrong? Will this ever work on an ordinary Comcast Xfinity plan, or must I pony up for Voice?