Unlocking the device with the latest update 6.0

Just bought this phone for $40 clean imei and ready to be activated with sprint. However, i tried unlocking it using different methods but none of the methods work at all. i don't want to risk bricking the device. I contacted Sprint and they told me i have to call the previous owner to request otherwise they won't unlock. I called the international tech team and they told me the same. The owner won't respond to my texts or calls and now I am just stuck with this device! I searched in here and found some members who are willing to do but none of them I could trust. One who wants to get full control of my laptop and pay him in advance $30, and the other guy want me to ship the phone, pay him $60 and just wait for it!! he's not my dad , he is not a relative, so thats a big NO. Please help if you know any method that may work , other sites won't unlock a CDMA phone especially Sprint devices. So I either find a way to unlock this ugly device, or just sell it. BTW Sprint told me i can have a prepaid account and wait 90 days then request and thats a no either. I don't know what to do at this point

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