You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I aid you?

USER: Myself Sandra Mitchell, I need to change my existing booking.

ASSISTANT: Sure, I can help you to change the details.

USER: Thank you.

ASSISTANT: May I know your name to check the ticket status?

USER: Sandra Mitchell here.

ASSISTANT: Ok, please give me a minute.

USER: Sure, take your time.

ASSISTANT: I have found your existing reservation. Can you please tell me your airport codes?

USER: ATL and LGA are the airport codes.

ASSISTANT: Ok, can you please tell me your changed travel dates?

USER: February 16 and 18 are the travel dates.

ASSISTANT: There is a flight in the UA airlines with the connection limit 1 and the ticket fare is 200. Can I proceed with this flight?

USER: Great! Please book this ticket.

ASSISTANT: Ok, I have changed the details and  booked a new ticket with the flight number 1000. Have a safe flight.

USER: Thank you for the assistance.

ASSISTANT: You are most welcome. Thank you for reaching us.