You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I'm Joseph Lee. Mistakenly I had booked a flight ticket with a price of 1000, could you please help me in changing my existing reservation?

ASSISTANT: Ok, let me check with your details.

USER: Ok.

ASSISTANT: Joseph, there is no reservation found under your name.

USER: Ok, thank you for your help.

ASSISTANT: Can I help you with anything else?

USER: No, I don't want any other help.

ASSISTANT: Thank you for choosing us.