You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you today?

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

ASSISTANT: Sure, can I have your name please?

USER: David Lopez here.

ASSISTANT: Ok, please wait for a while.

USER: Sure.

ASSISTANT: Thanks for waiting, there is no active reservation on your given name.

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

ASSISTANT: Thank you for opting us.