The old account would usually be removed when the owner is getting it ready to sell. Where did you buy it from, was it a legitimate retailer because it seems a little fishy to me like it could be a stolen phone but its not impossible for the owner to forget I suppose so in that case contacting the seller who would know who it belonged to and the original account holder would be more than happy to have their information removed from something they sold. Maybe samsung can comfirm with the account holder.
