A high-priced prostitute who usually works outcall from a home or office as opposed to getting customers on the street or at a brothel.

a female prostitute who can be hired by telephone

One who represents the upper end of the economic scale of prostitution by catering to a more affluent customer and generally making arrangements over the telephone. Since call girls do not actually walk the streets, their activities are not visible to either the public or the police.

Outcall provider, usually implies agency.

A prostitute who performs outcalls. Usually implies an agency.

A call girl or escort is a sex worker who (unlike a street walker or prostitute) is not visible to the general public. Nor does she usually belong to an institution like a brothel. One must summon her, usually by calling a telephone number—hence the name call girl.