You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, welcome to flight booking agency.

USER: I am Frank Johnson.

ASSISTANT: How may I guide you for today?

USER: The dates of concert is changed due to the adjustment of the singer dates. Can you change my reservation?

ASSISTANT: Sure, please give me a minute, I will check it out whether your reservation is existed or not.

USER: Ok.

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

USER: It's ok, anyway thank you for your help.

ASSISTANT: You are welcome. Thank you for reaching us.

USER: You are welcome.