You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am John Walker.

ASSISTANT: How may I support you today?

USER:  already have an reservation to attend a meeting, due to some problems meeting place has been changed. So I need a few changes in my reservation,.

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

USER: Ok.

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

USER: That's Ok, thanks for your assistance.

ASSISTANT: Thanks for availing us.