You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How can I assist you?

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

ASSISTANT: Yes, I can help you. Can you share me your name for checking?

USER: Thank you. Sure, my name is Deborah Turner.

ASSISTANT: I have found reservation on your name. Can you tell me your nearest airport codes?

USER: Sure, my airports codes are from OAK to PHL.

ASSISTANT: Ok, can I know your travelling dates?

USER: Ok, my dates of journey are from 05/15 to 05/17.

ASSISTANT: Give me a moment.

USER: Sure, I will wait.

ASSISTANT: Sorry to inform you that there are no flights found on your requested dates.

USER: Ok, no problem.

ASSISTANT: Thank you for consulting us.

USER: Thank you for your service.