content: Best Buy moved a ton of these Lumia 640 AT&T Go Phones on black Friday for $30 with no other requirements. I decided to get one to upgrade from my Lumia 521 because it's 512MB of system memory was holding back Windows 10 Mobile performance. Which now runs wonderfully on my Lumia 640. I already moved my 64GB mSD card to the new phone. The only down side in moving from the 521 to the 640 is that T-mobile has wifi calling for their handsets and hasn't made it available to the whole community. So I lost that feature when upgrading.