You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am David Green.

ASSISTANT: How can I aid you?

USER: Due to sudden change in the climate,  so I want to change my recent reservation. Could you please help me with this?

ASSISTANT: Sure,wait for a minute.

USER: Ok.

ASSISTANT: Thanks for waiting. Sorry, there is no reservation found on your name.

USER: Ok, no issues. Thank you for your information.

ASSISTANT: Thank you for availing us.