You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I help you?

USER: I want to change my recent reservation. Can you help me out?

ASSISTANT: May I know your name please?

USER: I am Jason Martinez.

ASSISTANT: I have found your reservation, for changing I need your airport codes?

USER: I want to travel from DEN to SFO.

ASSISTANT: On which dates you like to travel?

USER: I want to travel in the flight on Apr 01 and Apr 03.

ASSISTANT: Do you have any connection limit?

USER: I am looking for a direct flight.

ASSISTANT: Is there any other requirements?

USER: No.

ASSISTANT: I am sorry no flights found on your route.

USER: That's ok. Anyways, thank you.

ASSISTANT: Thank you for choosing us.