You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Emily Davis here.

ASSISTANT: How may I assist you?

USER:  Yesterday I booked a ticket to New York through your agency, your agent by mistakenly booked a ticket on wrong dates, so I want to change my reservation.

ASSISTANT: First I would like to apologise you for what was happened to you. Yes, I am here to help you again.

USER: Ok, that's fine.

ASSISTANT: Please give me a minute to check.

USER: Sure.

ASSISTANT: Sorry. There is no reservation is found in my database. Do you like to know anything else?

USER: No issues, thank you for your information.

ASSISTANT: You are welcome.