She needs to have maintenance from th building put in a second line, you cant run both services on the same line because of interference issues as well as the modem wont react well to power on the line, also I read someones post about frq levels as far as Comcast is concerened it is 5-1000 not 5-550
This is CABL.com posting #259268. Tiny Link: cabl.co/mbfBU