You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello. How may I aid you today?

USER: Due to health problems I want to change my existing reservation, can you please make some changes in the reservation?

ASSISTANT: Sure, I am glad to help you with that.

USER: Thank you.

ASSISTANT: May I know your name to search your reservation?

USER: I am William Lewis.

ASSISTANT: I have found your reservation, can you please provide your new journey airport codes?

USER: I want to start my journey from CLT to reach MSP.

ASSISTANT: Ok, may I know your departure and return dates of travelling?

USER: I want to depart on May 4th and return on May 6th.

ASSISTANT: Do you have any connection limit?

USER: I prefer a maximum number of one connection in between my journey.

ASSISTANT: Any other preferences do you have?

USER: No.

ASSISTANT: Please wait a moment to check the flights.

USER: Ok.

ASSISTANT: We regret to inform you that, there are no flights available for your journey with your requested dates of travelling.

USER: Ok, no issues. Thank you for your information.

ASSISTANT: Thank you for reaching us, have a great day.