How to break house phone?

Well, to make a long story short, my internet cuts when the house phone is calling or receiving calls. No one uses the house phone but my mom, and she is making me, my dad, and my brothers lives miserable because she wont stop talking (actually in one month she made my dad pay $1000 dollars phone bill...he broke down in tears). I want to figure a way to cut break or stop the house phone receiving calls, this has to be discreet and non visible, so i dont get any accusations. Also the phone is wired.