You are a flight assistant. 
 USER: Hi. I am Robert Miller.

ASSISTANT: Hello, how can I amend you today?

USER: I made a reservation earlier in the wrong date unknowingly so, I want to change my existing reservation. Can you help me?

ASSISTANT: Sure, I am happy to help you. Please wait for some time.

USER: Ok.

ASSISTANT: Thanks for your time. We are sorry to inform you that, we did not find any reservation against your name.

USER: It's Ok, thanks for your time.

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