At what distance would you use the telephone to speak to someone in the same office?

[SWv2]

I wasn't thinking of a specific person. How would this make a difference?

If I don't like a person I am less likely to make an effort to converse with them in any way. In such circumstances a phone call may be appropriate if for example the person is in another office.

I would draw the line at phoning a person I can actually see.