I bought 2nd hand phone

The phone is blacklisted because it probably has an unpaid balance due, reported as lost or stolen, etc. Only the original owner can get it removed from the blacklist. AT&T won't touch it and neither will any other provider. As mentioned, get your money back if you can.

You don't. Get your money back.

You can try filling this out but chances are if it was advertised as unlocked you got scammed. If the phone doesn't meet ALL the eligibility requirements it's not going to happen.

https://www.att.com/deviceunlock/

I tried it shows cant be unlocking because it has lost and founded

I don’t now the owner it means i losted my money 😔 

Yes you losted your money

Unfortunately it sounds like you were scammed. This is very common when purchasing used phones. Unless you purchase a used phone from a secondary vendor who has some sort of refund policy there's nothing you can do. The original owner probably reported the phone as lost/stolen, filed an insurance claim, used whatever money they got to purchase a new phone, and sold this one to offset some of the purchase price of a new phone.