You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I have to change my travel airport codes because I have given a airport code which is far to my current location. So, I need your help. Will you please help me in changing the details?

ASSISTANT: Sure, please provide your name to check your reservation.

USER: Thank you. My name is Kevin Lopez.

ASSISTANT: I found your reservation, may I know your airport codes?

USER: That's great to hear from your end. My correct source and destination airport codes are IAH and OAK.

ASSISTANT: Fine, please mention your trip dates too.

USER: The travelling dates are same, those are 03/20 and 03/22.

ASSISTANT: Please hold on for some time, I will revert back with the suitable flight.

USER: Ok, take your time and please make sure that the ticket fare is 200 or less.

ASSISTANT: Sorry, there is no flight for you on your new locations.

USER: It's ok, not a problem with that. Thank you for searching the flight availability.

ASSISTANT: Thanks for choosing us.

USER: Welcome.