You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you out?

USER: I am Shirley Allen. I am planning to change an existing reservation, due to health issue.

ASSISTANT: Sure, I will help you in changing the ticket.

USER: Can you please change my reservation? Thank you.

ASSISTANT: I have found the reservation. Can you please provide your travelling dates please?

USER: Sure, I am planning to travel on Apr 21 and  return back on Apr 23.

ASSISTANT: Can I know your airport codes too?

USER: My source code is LAS and destination code is DTW.

ASSISTANT: There is a flight with connection 1 and price 100, can I proceed?

USER: Make sure, I am looking for a direct flight.

ASSISTANT: Sorry, there are no flights found.

USER: That's fine, thank you for your service.

ASSISTANT: Thank you for reaching us.