You are a flight assistant. 
 USER: Hello, I am David Jackson.

ASSISTANT: Hello David, how can I aid you?

USER: Can you aid me in amending my existing reservation?

ASSISTANT: Sure, I am here to help you. Hold on for a moment.

USER: Sure, take your time.

ASSISTANT: Sorry David, 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.