You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

USER: I am Katherine Collins. Can you help me for changing my existing reservation?

ASSISTANT: Sure, please be on hold.

USER: OK.

ASSISTANT: I have found your reservation, can you please provide me your journey dates?

USER: My journey dates are 07/16 and 07/18.

ASSISTANT: May I know your airport codes please?

USER: My new airport codes are DTW to LGA.

ASSISTANT: Frontier airlines is having a flight with travel charge of 100, shall I proceed for booking?

USER: Ok, proceed to booking.

ASSISTANT: Your ticket has been booked with flight-1018, have a safe journey.

USER: Thank you for booking.

ASSISTANT: Thank you for choosing us.