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

ASSISTANT: Hello, how may I assist you?

USER: I want to do some changes in my journey dates. Can you help me?

ASSISTANT: Sure, hold on for a moment.

USER: Take your time.

ASSISTANT: Let me check. Sorry Mark, there are no flights reserved on your name previously.

USER: No issues. Thank you for checking.

ASSISTANT: Welcome. Thank you for choosing us.

USER: You are welcome.