Unknown callers?

Few days ago,
called one of my colleagues after office hours,
obviously her secretary has left,
she picked up the phone by herself,
the voice I recognize from the phone,
however,
acting like her secretary,
asking me who called,
at last,
she explained to me that,
after office hours,
she doesn't want to occupy her precious working time by unknown callers,
as her secretary could not handle the calls for her,
thus,
she needs to disguise other person pick up the phone!