caller
noun [ C ] uk/ˈkɔː.lər/ us/ˈkɑː.lɚ/
(PHONE)
（尤指给电台或电视台直播节目）打（进）电话的人
someone who makes a phone call, especially a member of the public who calls a radio or television programme while it is being broadcast
I'd just like to comment on what your previous caller was saying. 我只想就前一位打进电话的人所说的事情谈谈我的看法。
(VISIT)
来访者，拜访者
a visitor