You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello.

USER: Joshua Martinez here.

ASSISTANT: How may I help you?

USER: Due to sudden health issue, I am not able to travel in a flight on those date that I want to travel. So, I would like to change my reservation. Can you please help me out with that?

ASSISTANT: Joshua Martinez, I am here to help you for this. Let me check your reservation status in our records.

USER: Thank you, take your time.

ASSISTANT: Sorry for inconvenience, no reservation is found with your criteria.

USER: Oh! I think the ticket was not booked due to server issue. Anyway, thank you for the information.

ASSISTANT: Thank you very much for reaching our agency.

USER: Welcome.