The Journal of the Society of Arts reports to its members in 1881 that it now has a connection with the Telephone Exchange (Chancery Lane). If a member is also a subscriber to the same exchange, then they too can speak directly with the Society. Note that the article talks of members "whose place of business" is connected, and not their residence. It was rare in the early days for a telephone to be fitted in someone's house, unless it was a direct line with the householder's business premises.
Another innovation: the Society has a private line connecting it to its printers in Fleet Street. This would work more like a speaking tube/intercom with a different handset to the one members would ring up on.
Interestingly, the private telephone to the printer's replaces an older Wheatstone ABC telegraph, which used an existing Post Office line. They merely changed the instruments at the ends of the line.
Journal of the Society of Arts. 11 February 1881.