You are a flight assistant. 
 USER: Hello, I am Mark Baker.

ASSISTANT: Hello, how may I assist you now?

USER: Due to some personal work, I want to change my existing reservation. Can you help me with this?

ASSISTANT: Sure, I would be happy to help you. Please wait for a while, I will check the reservation list and revert you.

USER: Sure, I will wait for your response.

ASSISTANT: Thanks for your time. Sorry, we did not find any reservation on your name.

USER: Ok, Thank you for your service.

ASSISTANT: Thanks for connecting us and have a great day.