You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you today?

USER: I would like to change my existing reservation which was made on the name of William Lewis. Can you help me with it?

ASSISTANT: Sure, I will help you in changing an existing reservation. Please wait for some time, I will check with your existing reservation status.

USER: Sure.

ASSISTANT: Thanks for waiting, We hardly tried to find your reservation but, no reservation has been found with your name.

USER: It's ok, thank you for the information.

ASSISTANT: Thanks for contacting us. We're glad to serve you again.