Though we haven't yet seen an official announcement of the Lumia 640 being available for purchase from AT&T, it looks like it's on its way. A Reddit user has apparently purchased the AT&T GoPhone variant of the Windows Phoe from Walmart, signaling that an official announcement from AT&T can't be too far off.
What makes this interesting is that although AT&T officially launched the Lumia 640 XL in late June, the carrier has yet to list the Lumia 640 for sale on its website. It appears that at least one Walmart may have pulled the trigger on selling it a bit early. On the price front, it looks like the phone will come in at $80, which is a bit cheaper than other offerings from T-Mobile and Cricket.
In any case, if you're a GoPhone user looking to pick up a new Lumia 640, it may be worth taking a quick gander at your local Walmart.
Source: Reddit Thanks to Chuck for the tip!