You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I guide you today?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, can you please mention your name?

USER: Jason Collins here.

ASSISTANT: Sorry, no reservation found with your given name.

USER: It's ok, thank you.

ASSISTANT: Thank you for choosing us.