You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I want to change my existing reservation, can you please help me with this?

ASSISTANT: Sure, we are here to help you. On whose name, the reservation has been made earlier?

USER: Melissa Hernandez.

ASSISTANT: Please stand by.

USER: Sure.

ASSISTANT: Thanks for your time, there is no active reservation found in your name to change.

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

ASSISTANT: Thank you for choosing our services, we will try to serve you for the next time.