I have a Galaxy Tab 3 SM-T217A that I purchased used through Cowboom. I would like to unlock it for other carriers. What would be the easiest and cheapest way to do this? I tried the AT&T unlock request page, but I am not an AT&T customer and never have been, and obviously do not know the name of the person who last used this device.
I have investigated the myriad millions of device-unlock services on the net, but my particular device doesn't show up on the drop-down-menu lists of supported devices on most of them.