I'm interested in getting a 640 xl. I still have my old 520. And also using moto g. Not to happy with g. I've noticed that there are different RM models I know they are for at&t and unlocked, but is there a specific usa model or does it not matter. If so what model is the USA model. Everyone one I find on amazon, say unlocked international version. Please help me understand. Thank you.
I believe the RM-1065 and RM-1096 work with ATT. I myself purchased two RM-1096 (matte black and glossy white) from Amazon over the last week from
here and they work without any issues on ATT (LTE, mms, internet sharing etc, all is working). This version is unlocked and dual SIM. It is international and if you do not put your SIM card into the tray they will start setup in Chinese

. Once you pop in your ATT SIM the setup starts in english, will reboot with the new language and continue setup.
They will show LTE as 4G and speed tests show that I am getting similar speeds that I had with LTE on my previous L830.
edit: according to one reviewer the RM-1064 is also compatible with US LTE.
Both wife and I really like the 640XL
cheers