You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you?

USER: Can you please help me in changing my existing reservation?

ASSISTANT: Sure, can you provide your name?

USER: My name is Larry Smith.

ASSISTANT: Give me a minute for checking.

USER: Sure, take your own time.

ASSISTANT: Sorry, there is no reservation found under your name.

USER: Ok, not an issue. Thank you for providing information.

ASSISTANT: Thank you for opting us.