In most cases, account sellers are not who or what they claim to be. Like many other scammers, they may take money from you, but doesn't give you access to account, which you bought. Or they can give access to you, but then return it back by using a completely logical way - confirm to developers, that they are account owners. Because of that you may lose account and money what you spent on it.
Also, in general, deals about selling accounts goes through third-party resources. In the main, they connected with social networks accounts, with which game accounts was linked, not with accounts in the game itself. This fact frees us from the responsibility to the "buyer", because in sale of the accounts the game itself does not appearing. And third-party resources, such as Facebook pages, Google accounts + and so on, are not our jurisdiction zone, so we can't return access to the accounts, which you bought on this resources in any way.
So, do not trust scammers! And try to warn other players about don't getting into this similar situation! Refuse to sell your account and report about those, who do it!