You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Gary Parker.

ASSISTANT: How may I aid you today?

USER: Can you help me for changing my existing reservation?

ASSISTANT: Sure, I will help you with that.

USER: Thank you.

ASSISTANT: Please wait for a while.

USER: Ok, I will wait for your reply.

ASSISTANT: I am sorry to say that there is no reservation found.

USER: Oh! It's ok, no problem, thank you for your services.

ASSISTANT: Thank you for contacting us.