I want to see phone bills for the house and the cottage for that time period.
In 1961, many people still didn’t have phones so one would imagine fewer families had phones on the island than on the mainland (my family didn’t get one until ‘68 at the city house and never did get one at the farm). Considering the neighborhood was ritzy, the main house might have had a phone but it’s doubtful there would be one in the guest house/cabin/cottage.