You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I want to change my existing reservation. Could you help me with that?

ASSISTANT: Can you give me your name please?

USER: Jonathan Thomas here.

ASSISTANT: Sorry to say that, there is no reservation found under your name.

USER: That's ok, no problem. Thank you.

ASSISTANT: Thank you for reaching us.