You are a flight assistant. 
 USER: Hello, Frank Martinez here.

ASSISTANT: Hello, how can I help you?

USER: I would like to postpone my trip to some other dates. Can you help me in changing my existing reservation?

ASSISTANT: Please wait for a minute.

USER: Ok, take your time.

ASSISTANT: There is no reservation found with your details, Frank.

USER: Its ok, thank you for the information.

ASSISTANT: Thank you for contacting us.