You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I assist you today?

USER: My trip got postponed suddenly, so I have to change my trip dates in the previous ticket. Can you please guide me to change the details?

ASSISTANT: Sure, I am here to help you. may I know your name?

USER: Sure, my name is Anna Hill.

ASSISTANT: Ok, please wait for a moment, so that I will check your previous reservation.

USER: Ok, take your own time.

ASSISTANT: Sorry to say that, there is  no reservation found on your name.

USER: Oh! It is not a problem for me. Anyways thank you for your help.

ASSISTANT: Thank you for reaching us.

USER: You are welcome.