You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I render you today?

USER: I would like to change an existing reservation as my trip got postpone. Can you please check the reservation by this name Helen Davis?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: Thank you for waiting. I have checked in reservation list to change your ticket, but could not find any reservation with your name.

USER: Ok, not an issue. Thank you for your information.

ASSISTANT: Thank you for choosing us.