You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: My name is Charles Hall.

ASSISTANT: How may I help you?

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

ASSISTANT: Ok, wait a moment let me check your reservation status.

USER: Sure, I will wait for your response.

ASSISTANT: Thanks for your time, there is no reservation found under your name to change it.

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

ASSISTANT: Thanks for choosing us.

USER: Welcome.