That would depend on the situation. I wouldn't sit around chatting to girlfriends n the work phone but if my kids needed me I would definitely take their call. In general, though, I've always tried not to make or take personal calls at work.
I have but usually during lunch. A relative once called with some devastating news while I was at work. I broke down right at my desk. I cant say he should have waited but he probably could have given me an tip before he spilled it.