You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: I am Jacob Brown.

ASSISTANT: How may I assist you today?

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

ASSISTANT: Sure, please wait for a minute, let me check the reservation details.

USER: Ok.

ASSISTANT: I could not find any reservation with your name in our database.

USER: No issue. Thank you.

ASSISTANT: My pleasure.