Are the 2 lines in separate names?
So far you have only talked about phone lines, but your title says "Internet Lines". You do know that in this country phone & BB are 2 separate services and you need a phone line in order to get BB, although they are often packaged together.
Who is housemate getting his BB from?
Who are you getting your BB from?
1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 20 Meg WBC