You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you?

USER: I want to reach Houston on Sept 21 but previously I made a reservation on Sept 20, so I need to change my travelling dates. Can you help me with this?

ASSISTANT: Sure, may I know your name?

USER: I made a reservation by this name Nancy Carter.

ASSISTANT: Ok, please wait a minute.

USER: Sure.

ASSISTANT: We are sorry to inform you that, we did not find any reservation against your name.

USER: That's fine, thank you for your information.

ASSISTANT: Thank you for reaching us.