You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you at this moment?

USER: Myself Sarah Martin, I need to change my existing reservation. Could you please help me in changing the reservation?

ASSISTANT: Sure, I will help you with that.

USER: Sure, I will wait for your response.

ASSISTANT: Thank you for waiting. There is no previous reservation available under your name.

USER: Not an issue, anyhow thank you very much for your reservation.

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