You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you?

USER: I have planned to go for SFO , unfortunately the trip was postponed can you please change my existing reservation? Myself Sandra Allen.

ASSISTANT: Sure, please wait for a moment.

USER: Ok.

ASSISTANT: Sandra, there is no reservation found under your name.

USER: Ok, fine.

ASSISTANT: Do you have any other queries?

USER: No.Thank you for your help.

ASSISTANT: Thank you for communicating us.