You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. What service that you are seeking from our agency?

USER: Sandra Miller here. I want to change my reservation, can you help me?

ASSISTANT: Sure, I am glad to help you. Can you please provide your name to check your previous reservation?

USER: I already mentioned my name, it is Sandra Miller.

ASSISTANT: Ok. Sorry to inform you that, there is no reservation found with your name in our records.

USER: Ok, no issues, thank you for checking for the availability.

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