what if you cant get in touch with the previous owner?

i have an old i phone 6 that i bought , a long time ago , my wife used it for a long time , then i traded her a 6 plus for it then i erased it now it has an apple id on it that i dont know and no one can get in touch with the previous owner, i have called apple and they refuse to fix the phone to were i can use it . Is there anything i can do to get it back were i can use it ?Hate to throw it away.