You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you today?

USER: I am Mark Carter from Phoenix. I want to change my travel dates in my previous reservation. Can you please help me with that?

ASSISTANT: Please wait a moment, let me check with the details in our database.

USER: Ok, thank you for your positive response.

ASSISTANT: Sorry Carter, there are no active reservations with your given details.

USER: Oh! It's ok no problem. Thank you for your information.

ASSISTANT: Thank you for reaching our service.