Comcast cable worked for four months with main box connected to TV with HDMI cable. Now it stopped (as well as two other boxes) and the rep says that HDMI cable can't be used to connect TV to box unless I pay extra 9.99 for HD. I don't believe that. He says that the reason the two secondary boxes stopped working is because I have the TV connected to the main box with HDMI cable and don't pay for HD service. I don't want HD service, just SD. What's the problem?