You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How can I serve you today?

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

ASSISTANT: May I know your good name please?

USER: My name is Raymond Jones.

ASSISTANT: Just hold on a moment.

USER: Sure.

ASSISTANT: We found a reservation with your given name in our records. Can you please mention your airport codes?

USER: My travelling airport codes are DEN to IAH.

ASSISTANT: When you are planning to make your journey?

USER: My travelling dates are July 21 and July 23.

ASSISTANT: Please provide your specifications.

USER: I need a connecting flight.

ASSISTANT: Unfortunately we did not find any flight on your route according to your given dates.

USER: That's ok, thank you for checking.

ASSISTANT: Thank you for choosing us.