You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I guide you today?

USER: My name is John Hernandez. I would like to change an existing reservation. Can you help me.

ASSISTANT: Sure, I will help you with that. Please wait for a minute, I will get back to you.

USER: Sure, take your time.

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

USER: No problem. Thank you for your time.

ASSISTANT: Thank you for reaching us.