You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello,.

USER: I am Lisa Evans.

ASSISTANT: How can I be at your service?

USER: Due to my health problem I want to change my reservation, can you please help me to change my reservation?

ASSISTANT: Sure, I am here to aid you. Please wait for a second.

USER: Ok.

ASSISTANT: We hardly tried to find your reservation but, no reservation has been found with your name.

USER: Ok, no problem. Thanks for your kind service.

ASSISTANT: Thanks for your approach, hope to serve you again.