You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Helen Roberts here.

ASSISTANT: How may I guide you today?

USER: Due to sudden work, I need to change my reservation. Can you please help me with it?

ASSISTANT: Sure, I will help you with that. Please wait for a minute.

USER: Ok.

ASSISTANT: I am sorry to say that there is no reservation found under your name.

USER: Ok, not an issue. Thank you.

ASSISTANT: Thank you for reaching us, have a great day.