You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I assist you today?

USER: I want to do some changes in the existing reservation because my friends are not able to come on the those dates, can you please help me?

ASSISTANT: Sure, I will help you with changing the reservation. Please provide me your good name for verification.

USER: Myself Donna Martin.

ASSISTANT: Ok, please give me a moment to check previous reservation status.

USER: Ok.

ASSISTANT: Thank you for waiting. Sorry Donna, there is no reservation found under your name. Thank you for choosing us.

USER: Ok, that's fine.Thank you for the information.

ASSISTANT: Most welcome. Have great day.