You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I serve you at this moment?

USER: I am looking to change the travel dates in the past ticket. Can you please help me to do that?

ASSISTANT: Sure, I will help you. Please send your travelling dates. Ok, please wait for a moment. May I know your name please?

USER: Ok, take your time. My name is Angela Green.

ASSISTANT: Sorry, there is no reservation existing on your name.

USER: It's ok, thank you for your time.

ASSISTANT: You are welcome, have a nice day.