iPhone 8 Plus

Hello.

I've just bought iPhone 8 Plus, unfortunately its no longer available from Apple, so I had to get one from company, that they providing "brand new" iPhones from network providers, after they upgraded offer to newest models of iPhone, and got rid of the old ones.

So my question is, how can I confirm that my "brand new" iPhone is really new, or has been refurbished, or even came from outlet after repair.

Please help me out with this one, I really like that model, I want to keep with that one.

I've tried IMEI checker, but it's not the point. I know that it's legit iPhone, but is it really new or just has the past that I would like to know about.

Thank You for any advices!