You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you today?

USER: I would like to change my existing reservation as my appointment with my doctor got postponed. Can you help me with it?

ASSISTANT: Sure, I will help you to change your reservation. May I know your good name?

USER: My name is Melissa Collins.

ASSISTANT: Please wait for a while.

USER: Sure.

ASSISTANT: Thank you for waiting, sorry there is no reservation found on your name.

USER: Thank you for the response.

ASSISTANT: Thank you for visiting us, we hope see you again.