You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you today?

USER: I want to change my existing reservation which is done recently due to some problems, can you please help me?

ASSISTANT: Sure, please mention your name.

USER: Sure, my name is Robert Garcia.

ASSISTANT: Please wait a moment.

USER: Sure.

ASSISTANT: Sorry Garcia, there are no active reservation on your given name.

USER: Ok, that's fine. Thank you for your service.