You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I serve you?

USER: I need to change my existing reservation, Can you please help me with that?

ASSISTANT: Yes, I am glad to serve you with that. Could you please tell me your full name?

USER: Melissa Brown here.

ASSISTANT: Ok, please give me a minute.

USER: Sure.

ASSISTANT: I am sorry to inform you that, there is no reservation found with your name to change the ticket details.

USER: Ok, no problem. Thanks for your information.

ASSISTANT: You are most welcome. Thank you for choosing our travel agency.