You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

USER: Can you help me change my existing reservation which was made on the name of Barbara Young?

ASSISTANT: Sure, wait a moment I will check the reservation list.

USER: Sure.

ASSISTANT: Thanks for waiting, unfortunately there is no reservation found by this name.

USER: Ok, thank you for the information.

ASSISTANT: Thanks for choosing us.