You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I assist you today?

USER: As my plans to visit Dallas has postponed, I would like to change my existing reservation. Can you please help me with this?

ASSISTANT: Ok, I will help you in changing your reservation. May I know your name please?

USER: My name is Benjamin Roberts.

ASSISTANT: Sorry Roberts, I have not found any reservation by your name in our database.

USER: Ok, not an issue. May be my friend has already changed my reservation. Thank you for your information.

ASSISTANT: Thank you for contacting us and have a good day.