You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how may I address you?

USER: I am Gregory Hill. I want to change my reservation due to health problem, can you help me?

ASSISTANT: Sure, please give me a moment. I will check the current status and revert to you.

USER: Ok.

ASSISTANT: We found a reservation by your name. Can you please share your new travel dates?

USER: My travel dates are 03/26 and 03/28.

ASSISTANT: Please provide me your airport codes as well.

USER: My airport codes are from IAD to OAK.

ASSISTANT: Ok, please wait.

USER: Sure.

ASSISTANT: We found a flight with the fare of 800. Is that fine?

USER: My price limit is 200.

ASSISTANT: Ok, let me check again.

USER: Sure.

ASSISTANT: Sorry, currently there are no cheaper flights available on your route.

USER: No problem, thanks for your information.

ASSISTANT: Thank you for choosing us.