You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: Actually, I want to change my existing reservation due to some problem, can you please help me in this intent?

ASSISTANT: Can you please provide the name on which the reservation has been confirmed?

USER: Sure, my name is Jacob Martin.

ASSISTANT: Sorry, there is no reservation found by your name.

USER: Ok, no problem. Thank you for your service.

ASSISTANT: Thank you and have a nice day.