Help! Voice mobility lines: Calling 2nd voice line rings 1st line!

Hello,

I have a new business voice mobility service setup since last month with 2 voice mobility lines. I am using the first for the main phone and the second for the fax. However when I call the 2nd number, it always calls the first line as well because the phone rings as well as the fax. This is a problem because the the phone operator picks up the phone and prevents the fax from receiving. If I disconnect the phone completely and call the 2nd line, then only the fax machine picks up the 2nd line call as expected.

Why is this occuring? I have tested all my patch panel connections and checked that they are all independent. I have tried switching around connections to the 4 jacks of the EMTA modem to see what is going on but it does not make a difference. I do not have call forwarding setup on the 2nd line (I have not touched its features at all). 

Do I have a defective emta modem or did Comcast not provision the lines correctly? Or is there some automatic setup that links the phone lines together or something? Please help me separate out the two phone lines to be completely independent. Thanks.