You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I help you?

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

ASSISTANT: Sure, please share your name to find current reservation.

USER: Sure, my name is Anna Martin.

ASSISTANT: I found reservation on your name please share your source and destination airport codes.

USER: Ok, my airports codes are from AUS to DTW.

ASSISTANT: What are your new travelling dates?

USER: Sure, my dates of travel are from 08/17 to 08/19.

ASSISTANT: I am sorry, no flights available on given dates from you.

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

ASSISTANT: Thank you.