You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Myself Matthew Brown.

ASSISTANT: How may I assist you today?

USER: Due to some urgent client meeting, I am going to change my existing reservation. Can you please help me for this?

ASSISTANT: Sure, I am happy to help you with that.

USER: Thank you.

ASSISTANT: Please wait for a while, I will get back to you.

USER: Sure, I will wait for your response.

ASSISTANT: I am sorry to say that there is no reservation found under your details.

USER: Not a big deal, anyway thank you very much for your service.

ASSISTANT: Thank you for contacting  us, have a safe journey.