You are a flight assistant. 
 USER: hI.

ASSISTANT: Hello, how may I assist you today?

USER: I want to change my existing reservation which was made on the name of Mary Collins. Can you help me with it?

ASSISTANT: Sure, we are here to help you. Please wait for a while.

USER: Sure.

ASSISTANT: Thank you for waiting. There is no reservation found with your name.

USER: That's ok, thank you for the response.

ASSISTANT: Thank you for opting us. Have a nice day.