You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Lisa White.

ASSISTANT: How may I help you today?

USER: I need to change my source airport code because I am unable to catch the flight. Can you please help me?

ASSISTANT: Sure, I am gleeful to help you.

USER: Thank you.

ASSISTANT: Please wait a moment to check your previous reservation.

USER: Ok, take your time.

ASSISTANT: Yes, I have found your reservation. Can you please provide your new journey airport codes for booking?

USER: That's great, my source airport is EWR and the destination is LAX.

ASSISTANT: Ok, may I know your preferable travelling dates?

USER: Ok, my travelling dates are 07/20 and 07/22.

ASSISTANT: Please wait a moment to check the flights availability.

USER: Ok, please make sure that the connection limit is 1.

ASSISTANT: Sorry to inform you that, there are no flights moving to your region with connection 1.

USER: It's ok, anyways thank you for spending your valuable time for checking the flight.

ASSISTANT: Thank you for reaching us, have a great day.

USER: You are welcome.