You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how can I help you today?

USER: My name is Sandra Hall. I want to change my arrival day in my existing reservation, can you help me?

ASSISTANT: Give me a moment, let me check your details.

USER: Ok.

ASSISTANT: Sorry, I didn't found any reservation basis on your details.

USER: It's ok, no issues.

ASSISTANT: Thank you for reaching us.

USER: Thank you.