You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello.

USER: Andrew Phillips here.

ASSISTANT: How can I assist you today?

USER: Suddenly, I have changed my plans. So, can you change my reservation?

ASSISTANT: Sure, please give me a moment.

USER: Ok.

ASSISTANT: Your reservation is found. Please mention your airport codes that you want to travel.

USER: My airport codes are from ORD to SEA.

ASSISTANT: Will you mention your travelling dates please?

USER: My travelling dates are from 12/28 to 12/30.

ASSISTANT: There is no flights found under your preferable details.

USER: It's ok. Thank you for checking.

ASSISTANT: Welcome, have a great day.