I Hope You Brought Coins
As would occasionally happen back in the day, when guests came to visit at Sutton Place - be they businessmen or workmen - they might use the telephone. Sometimes, those calls might be long-distance or to overseas, which you'd best believe J.P. was not about to foot the bill for.
His answer? He placed dial-locks on all of the regular telephones, and had a payphone installed for people to use at their own financial freedom!