You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I aid you today?

USER: Can you amend my existing reservation?

ASSISTANT: Sure, I am here to help you. May I know on whose name the ticket has been reserved formerly?

USER: I am Patrick Robinson.

ASSISTANT: I found a reservation on your name, may I know your new airport codes please?

USER: Search for the flights from PHL to IAH.

ASSISTANT: Ok, can you please mention your travelling dates?

USER: I am planning to start on Apr 3rd and return back on Apr 5th.

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

USER: I prefer to travel in direct flight.

ASSISTANT: Sorry Patrick Robinson, 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.