You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Daniel Allen.

ASSISTANT: How can I assist you today?

USER: I would like to change my existing reservation, so can you help me for that?

ASSISTANT: Sure, please allow me a moment to check for the availability of flight. Daniel, there is no reservation found under your name.

USER: Oh! It's ok, no problem. Thank you for your services.

ASSISTANT: Thank you for contacting us.