Bought Xbox one and it has a console ban

You would have to try contacting the person you bought it from to see if you can return it, but there would be no way to have it unbanned.

The warranty on a second-hand Xbox console is void, and the purchaser assumes the risk for any previous modifications or unauthorized activity. Even if the console’s ownership has changed, the console may still be subject to a ban. If you purchase a console
that has been previously banned you will not be able to connect to Xbox Live, and the ban will not be lifted as a result of the change in ownership. We recommend customers who believe they have not committed actions on the service to warrant a ban to contact
previous owners or users of the console.

If you have purchased or intend to purchase a second-hand Xbox 360, you can check its current ban status by entering its serial number into the Console Check Tool: http://enforcement.xbox.com/Home/ConsoleCheck.

There is no way to unban a banned console.

You will have to contact the seller of the console, and if he didn't tell you that the console was banned before purchase, you should demand your money back.

With every used Xbox console you buy it's always "buyers beware". Always let the seller demonstrate the console and connect to Live, so you can check that the console is working and isn't banned.

If you buy a used console without checking, you can run into unpleasant surprises like that.

If it says the console has been banned all you can do is try taking it back and buying a new one. Console bans are not reversed even if you bought it second hand.

Well I can tell you one thing. If the person that you bought that console from was "Modding" using that console, xbox can not do anything about that. Once an xbox has been Perma-Banned there is nothing anyone can do for you. The only real thing you can do
is just call the person you bought the console from and ask for your money back.

- TG TRYHARD