Info 2 Reset Note 3 Completely

Here is my deal. I have to send in my note 3 to at&t or samsung when I get the replacement phone that they are sending me. I have previously rooted my phone, but I don't think it is rooted anymore. So Knox status is 0x0 and the other thing that is knox related is also 0x0, but I still have the device status as custom. Is this going to void my warranty if I send it in like this?

The question: How do I get rid of the custom status of my device and is there anything else that I need to check before sending it in.