You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I would like to change my reservation due to some health issues, can you please help me out with that?

ASSISTANT: Sure, I can help you in changing the reservation details. Could you please let me know on which name you have booked the ticket?

USER: Reservation has been done under the name Mark Hill.

ASSISTANT: Ok, I need few seconds to check your ticket status. So, can you please provide me sometime?

USER: Sure, I will wait for your response.

ASSISTANT: When I have checked your ticket status, I have not found any reservation which is done under your name. Sorry for that.

USER: Ok, no problem. Anyway thank you for checking out.

ASSISTANT: You are welcome. We will serve you better in the next time. Thank you for opting us.