What do you think caused the phone (and eventually the power) to go out?

The ghouls had no concept of phone/power. Some say that the first ghoul pulled the phone lines out but wasn't that the clothesline?

I'm guessing that the corpse upstairs was perhaps someone who had died long before the epidemic began and no one knew about it. That's why the phone was disconnected. But the power, what caused the power to go out?