You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello, how may I help you today?

USER: I made a reservation to go for a trip with my friends, but  due to my busy schedule I want to change my reservation. Can you please help me with the same?

ASSISTANT: Sure, we are here to help you.

USER: Thank you.

ASSISTANT: May I know your name to check the reservation list?

USER: Sure, my name is David Mitchell.

ASSISTANT: Please wait a moment, I will check your details and get back to you.

USER: Sure, take your time.

ASSISTANT: David Mitchell, we are sorry to inform you that there is no reservation exist on your name to do modifications.

USER: Not an issue, thank you for checking it.

ASSISTANT: Thank you for contacting us. Have a nice day.