You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I help you?

USER: My name is Sarah Rodriguez, and I want to change my existing reservation?

ASSISTANT: Sorry to say that Sarah, there is no reservation found under your name.

USER: OK, no problem.

ASSISTANT: Thank you for reaching us.

USER: Thank you, for helping me.

ASSISTANT: Welcome, have a nice day.