You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: Can you please help me to change my existing reservation, due to my plan with my friends has been postponed?

ASSISTANT: Sure, can you please provide me your name to check the reservation?

USER: Sure, please check my reservation on the name of Dennis Mitchell.

ASSISTANT: Sorry, there is no reservation with your given name.

USER: Ok, thank you.

ASSISTANT: Thank you for reaching us.