You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: My name is Jack Garcia. I want to do some changes in my existing reservation. Can you help me for that?

ASSISTANT: Ok, wait a moment please.

USER: Sure, I will wait for your response.

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

USER: That's ok, thank you for checking.

ASSISTANT: Thanks for choosing us.

USER: Welcome.