Green’s Dictionary of Slang

call house n.

[SE call (on), to visit + house n.1 (1)]

1. [early 18C+] (also house of call) a brothel to which men can come without making any prior appointment.

2. [1910s+] a hetero- or homosexual brothel to which women or men are summoned by telephone after they have been selected, via some form of visual ‘menu’, by the male clientele; thus call trade, prostitution arranged on this basis.