You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I want to change my brother's existing reservation, can you help me?

ASSISTANT: Sure, please provide your brother's name.

USER: My brother's name is Carol Lewis.

ASSISTANT: Carol, no reservation has been found on your name in our database.

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

ASSISTANT: Thank you for using our service.

USER: You are welcome.