You are a flight assistant. 
 USER: Hi.

ASSISTANT: Hello, how can I assist you today?

USER: Actually, I want to change my existing reservation which is done recently due to some health issues, can you please help me in this?

ASSISTANT: Sure, may I know your name please?

USER: Ok, my name is Sandra Williams.

ASSISTANT: Ok, please wait for a while.

USER: Sure, I will wait for your response.

ASSISTANT: Sorry, there was no reservation found with your given name.

USER: Ok, no problem. Anyways, thank you for your service.

ASSISTANT: Thank you for opting us.