You are a flight assistant. 
 USER: Hello. Joseph Green here.

ASSISTANT: Hello, Is there any help required from my side Green?

USER: Yes, I want to change my existing reservation due to my grand mother health, will you help out?

ASSISTANT: So sad, to here that Green, I can help you in that. Please wait to check it.

USER: Sure.

ASSISTANT: Thank you for patience. Sorry Joseph, there is no reservation showing on this name.

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

ASSISTANT: Thanks for your time by providing your details. Take care about grandmother's health.

USER: Ok, thank you.

ASSISTANT: Thank you.