You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you at this moment?

USER: I want to change my reservation which is done recently due to some problems, can you please help me?

ASSISTANT: Sure, I am happy to help you with that.

USER: Thank you.

ASSISTANT: Can I have your good name please to check your reservation status?

USER: Sure, my name is Angela Lewis.

ASSISTANT: Ok, please wait a  moment.

USER: Sure, I will wait.

ASSISTANT: Yes Angela Lewis, your reservation has found so please let me know your travelling dates.

USER: Sure, my planned dates of journey are from Jan, 19 to Jan, 21.

ASSISTANT: Ok, please let me know the airport codes of your locations.

USER: Ok, my respective airport codes are from LAX to OAK.

ASSISTANT: Do you have any more specifications?

USER: Yes, I need a business class.

ASSISTANT: Ok, please wait a moment.

USER: Sure, I will wait.

ASSISTANT: Sorry Angela Lewis, no flight is available to you in business class.

USER: Ok, no problem. Thank you for your service.

ASSISTANT: Thank you for choosing us, have a good day.