You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, do you need any help from us?

USER: I want to change my trip dates of existing reservation as my plan to go for an adventure trip got postponed. Can you help me?

ASSISTANT: Sure, could I have your name please?

USER: I am David Hall.

ASSISTANT: Ok, please allow me a moment.

USER: Sure.

ASSISTANT: Sorry, there is no reservation with your name in our portal to make changes.

USER: Ok fine, thanks for your response.

ASSISTANT: You are welcome, have a great day.