You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: I am Jacob Hill.

ASSISTANT: How can I help you today?

USER: I want to change my existing reservation, due to some health issue. Can you please help me?

ASSISTANT: Sure, I will help you to change your reservation.

USER: Thank you.

ASSISTANT: Happy to say this, I found your reservation. Can you please help me with your new travelling airport codes?

USER: Sure, my airport codes are from OAK to MSP.

ASSISTANT: On which dates you want to travel?

USER: My travelling dates are 06/07 and 06/09.

ASSISTANT: Please wait a moment.

USER: Ok, take your time.

ASSISTANT: Sorry, no flights are available on your route.

USER: It's ok, thank you for your information.

ASSISTANT: Welcome, have a nice day.