You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Debra Thomas.

ASSISTANT: How can I help you?

USER: Actually, I want to change my  journey codes. So, can you please help me in changing my existing reservation?

ASSISTANT: Sure. Sorry to inform you that there is no reservation found on your name.

USER: That's fine. Thank you for your information.

ASSISTANT: Thank you for reaching us. You are welcome.