You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I help you?

USER: I am planning to meet my colleagues who are staying in Oakland, but I met with an accident my planning to meet my colleagues has been postponed.So I would like to change my existing reservation. Can you please help me in changing?

ASSISTANT: Sure, may I know your name please?

USER: Robert Mitchell.

ASSISTANT: Wait a moment.

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

ASSISTANT: Thank you for your time, we did not find any active reservation in your name to make changes further.

USER: Ok, no issues. Thank you for your information.

ASSISTANT: Thank you for choosing us.