Simlock Iphone

Hello,I bought a few days ago an iPhone 3GS (Un friends give me, but unfortunately when I inserted my SIM card (Mobile Vikings) I noticed that this phone was simlock after more research I noted that the iPhone is stuck on a network.

I need help because I am the fourth owner, so I do not know the principal owner, this forum is my last solution to finally use my iphone Image may be NSFW.
Clik here to view.

here is the IMEI: ******and serial number: 87******3NPThank you in advance for your future support which in my eyes is very important.

Thanks

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