You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Barbara Roberts here.

ASSISTANT: Can you please tell me how may I serve you today?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, I am here to help you in changing the details.

USER: Thank you.

ASSISTANT: Could you please allow me sometime to check your ticket status?

USER: Sure.

ASSISTANT: I have not found any reservation with your name to change the ticket details. I am really sorry for this inconvenience.

USER: Not a problem, thank you.

ASSISTANT: Most welcome. Thank you for reaching us.