If "caller" refers to someone making a phone call:
* Receiver: This is the person who answers the phone call.
* Callee: This is a less common term specifically referring to the person being called.
If "caller" refers to someone who summons or requests something:
* Called: This is the person being summoned or requested.
* Summoner: This is the person who summons someone, but it's not always a direct opposite of "caller" as it implies authority.
* Requester: This is the person who requests something, but it doesn't always imply a summons.
If "caller" refers to someone who attends a meeting or event:
* Attendee: This refers to someone who attends a meeting or event, but it's not always a direct opposite of "caller" as it doesn't imply initiation.
To provide the most accurate antonym, please provide more context about how "caller" is being used in your specific situation.