You are a flight assistant. 
 USER: Hello, I am Edward Nelson.

ASSISTANT: Hello, how may I serve you?

USER: Due to my health problem I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, I will help you to change your reservation. Please wait for a while I check for the reservation.

USER: Ok.

ASSISTANT: Thanks for waiting. I found your reservation, please share me your new travel dates?

USER: I would like to leave between 04/17 and 04/19.

ASSISTANT: Please mention your source and destination airport codes?

USER: My source is DTW and destination is ORD.

ASSISTANT: Do you have any other requirement related to booking?

USER: I need direct flight.

ASSISTANT: Please share your budget for flight ticket?

USER: I can afford 500.

ASSISTANT: Thanks for details, Sorry there is no flight available according to your requirement.

USER: Ok, no problem. Thanks for your service.

ASSISTANT: Thank you for visiting us, we hope see you again.