To deal with or attend to people, customers, complaints, etc.; to receive callers or visitors and handle matters appropriately.
受付の人が来客に応対した。
The receptionist attended to the visitor.
苦情には迅速に応対する必要がある。
Complaints need to be handled promptly.
コールセンターで電話応対の研修を受けた。
I took phone-handling training at the call center.