Mm, I'm afraid we've never been given any kind of option of calling out of here. All we have are these devices for making calls internally.
And you can just have an apartment. Just make sure no one is already living there and just start. There's really no system to it. There are empty houses too or you can take a room in the shelter. There's a store you can get items for it or you can request specific things from Acumen. Everything is free.