You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you today?

USER: I have planned a small hangout trip with my friends, but someone don't have manage his leaves, so we want to change our existing reservation. Can you please help me with that?

ASSISTANT: Sure, I will help you with that. Please give me a moment.

USER: Sure.

ASSISTANT: May I know your good name for verification?

USER: My name is Barbara Green.

ASSISTANT: Sorry Green, your reservation has not found in reservation list to change it.

USER: Ok, not an issue.

ASSISTANT: Thank you for reaching us.

USER: Thank you.

ASSISTANT: Have a good day.