You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

USER: I am Rebecca Miller. I want to change my reservation due to health problem, can you help me?

ASSISTANT: Ok, please can you wait a moment?

USER: Sure.

ASSISTANT: Ok, thank you for waiting. Sorry, there is no reservation been found on your name as per our records.

USER: No problem, thanks for checking.

ASSISTANT: Thank you for choosing our service.