My phone show blacklist

Someone, probably the person you bought it from, has reported the iPhone to a cell carrier as stolen and it's now been put on the blacklist. This is a rather common scam when someone sells a phone and then reports it as lost or stolen so they can claim the insurance. Only your cell carrier can get that blacklist block removed, if even they can. You will need to contact your cell carrier's support resources and try to work through the problem with them. There is nothing anyone here or at Apple can do to help.

Regards.

Haider1m wrote:

I buy from third party iam from pakistan and I import this phone from usa soo iam the first owner i active this but its show stolen when i try to unlocked his carrier

That phone is not going to be useful until the carrier that added it to the blacklist removes it from the blacklist.

Which they are unlikely to do for you. They might remove it for the original owner.

Your sole path, and it’s not a good one: contact the third party you bought it from, and request refund or resolution.

Or in fewer words, you seem to have gotten scammed.

Related: The All Too Common SAD Reality of Buying a used iPad/iPhone - Apple Community

Where did you purchase the phone? From Apple, an Apple Authorized iPhone reseller, or a 3rd party supplier not directly affiliated with Apple?