Bought Galaxy s3, turns out its blacklisted topic

Hey I bought a galaxy s3 off someone at university, it has the optus logo when booting up and I was told it was a optus phone, I got a new optus sim put it in and its saying the handset has been locked by optus, so its been stolen i guess and I guess the seller wont give me my money back... So am i able to unlock the phone or is it screwed or can i unlock the phone from the optus network and use another phone provider?

[Q] Help with D803 blacklisted can it be fixed? topic

I just bought a LG G2 D803 off kijiji and have found out the hard way it has been blacklisted. Does anyone have a guide on fixing this or has anyone successfully changed there imei on these models? I am rooted on 4.2.2 stock

I have a att htc one phone and its been blacklisted is there anyway around that for I topic

Sent from my SGH-M919 using xda app-developers app

What should I do with this blacklisted phone? topic

Long story short, this kid I know found an Optimus L5 outside, last summer I think, and instead of reporting it, he kept it. He used it for some time until the phone got blacklisted here in Europe. He gave it to me now. It is already blacklisted, so it can not be used as a phone. What should I do with it? Should I take it to the police? Or if I keep it, then can someone track it if I use GPS or WiFi? I already put new firmware on it, if that helps.

Thanks!