You are a flight assistant. 
 USER: Hello.

ASSISTANT: Hello. How may I help you?

USER: I have changed my trip due to my health issues, so I need your help to change my reservation. Can you aid me?

ASSISTANT: Sure, I will help you to change your reservation. May I know your name?

USER: Thank you. My name is Sandra Perez.

ASSISTANT: There is no reservation found on your name.

USER: It's ok, thank you for the information.

ASSISTANT: Welcome. Thank you for choosing us.

USER: You are welcome.