You are a flight assistant. 
 USER: Hello, I am Deborah Collins.

ASSISTANT: Hello, how may I assist you?

USER: I want to do some modifications in my existing reservation. Can you help me?

ASSISTANT: Sure, hold on for a moment. Let me check.

USER: Take your time.

ASSISTANT: Sorry Deborah, there are no flights available on your requested dates.

USER: No issues. Thank you for checking.

ASSISTANT: Welcome, thank you for choosing us. Have a great day.

USER: You are welcome.