You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am David Clark.

ASSISTANT: How can I assist you David?

USER: Due to change in my plans to visit Charlotte, can you please help me in changing my existing reservation?

ASSISTANT: Sure, please be on hold.

USER: Sure, I will wait for your response.

ASSISTANT: David, there is no reservation found under your name to do changes in that.

USER: Ok, not an issue. Thank you for providing information.

ASSISTANT: Thank you for choosing us.