Guy promises to 'always be there' for girl; roommate furious about late night calls.

My friend and I rented a room together for our first semester of college. I moved from a different city and we're going to a school in his home city. There was a friend I left behind when I moved out of college who has mental issues and was dependent on me for support.

She was distraught that I was moving, but I made a promise to her that I would always be available to talk to any time of the day or night. Because of this I never put my phone on silent.

She calls a lot late at night because of her schedule, that's when she's able to talk. I don't mind so much because I'm a night person and have insomnia. My friend/roommate however has started complaining that it wakes him up and asks if I could put my phone on silent at night. I said no.