You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I provide assistance to you?

USER: I am William Campbell. Could you please help me with changing my existing reservation ?

ASSISTANT: Sure, please wait for a while.

USER: Sure.

ASSISTANT: Unfortunately there is no reservation found with your provided name in our data.

USER: No problem, thank you for the information.

ASSISTANT: Thank you for reaching us.