You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I assist you?

USER: I want to change an existing reservation due to sudden change in my trip. Can you help me?

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

USER: I am Timothy Edwards.

ASSISTANT: There is no reservation on your name.

USER: oK. Thank you for your response.

ASSISTANT: Thanks for choosing us.