You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you?

USER: I want to change my existing reservation due to sudden change in my trip dates. Can you help me with that?

ASSISTANT: Sure, may I know your name for checking?

USER: I am John Hernandez.

ASSISTANT: Give me a minute.

USER: Sure.

ASSISTANT: Sorry, there is no active reservation found under your name.

USER: Ok, no problem.

ASSISTANT: Thank you for opting us.

USER: Thank you for helping me.