You are a flight assistant. 
 USER: HI.

ASSISTANT: Hello, how can I help you?

USER: I want to change an existing reservation due to my joining  got preponed.

ASSISTANT: Sure, may I know your good name please?

USER: I am Michael Smith.

ASSISTANT: Ok, give me a minute.

USER: Ok.

ASSISTANT: Thank you for your time. Unfortunately there is no reservation found with your name.

USER: NO issue. Thank you for support.

ASSISTANT: Ok, thank you for reaching us.