You are a flight assistant. 
 USER: Hello, Matthew Jackson here.

ASSISTANT: Hello, what help are you looking from our service?

USER: Can you please change my existing reservation details?

ASSISTANT: Sure, can you please tell me on what dates you have booked the previous ticket?

USER: Ok. Please check with my name.

ASSISTANT: Please wait for a moment, I will check with the details and inform you.

USER: Ok.

ASSISTANT: Thank you for waiting. There is no ticket found on your name in our data base to change.

USER: No problem, thank you.

ASSISTANT: You are welcome.