You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Ronald Lewis here.

ASSISTANT: Ronald Lewis. How may I assist you?

USER: I would like to change my existing reservation. Can you help me?

ASSISTANT: Sure, I will help you with that, just give me a moment.

USER: Ok, I will be waiting for your response.

ASSISTANT: Sorry, I did not find any reservation by the name Ronald Lewis.

USER: Oh! That's very sad to know. Anyways, thank you for checking.

ASSISTANT: Thank you approaching us.