caller

noun

the person who convenes a meeting
“who is the caller of this meeting?”
someone who proclaims or summons in a loud voice
“the callers were mothers summoning their children home for dinner”
a person who announces the changes of steps during a dance
“you need a fiddler and a caller for country dancing”
caller-out
the bettor in a card game who matches the bet and calls for a show of hands
an investor who buys a call option
a social or business visitor

company
the person initiating a telephone call
“There were so many callers that we finally disconnected the telephone.”
caller-upphoner

adjective