This information is all wrong. Pretty much every SIM that AT&T gives out these days is a secure / payment SIM, but the only company/service that used secure SIMs doesn't exist any more.
The real answer though is that Microsoft doesn't support NFC payments at this time.
Yes, there was one carrier in France that supported NFC payments with WP 8.0, and then Softcard had an app for a month or two that let you use your phone for payments in the US... but Softcard is completely defunct now, and Microsoft still has no solution.
It's rumored that sometime soon Microsoft will have a system ready to go for W10M (using Host Card Emulation, basically the same technology that Google Wallet uses), but nothing has been announced. And then, only a small handful of W10M devices actually have an NFC implementation that allows for HCE. (
How to write an NFC Host Card Emulation (HCE) app with Windows 10 for Mobile - NFC Team Blog - Site Home - MSDN Blogs)
The 640XL though is specifically called out as supporting HCE, so really it's just a matter of waiting for Microsoft to actually roll out their system.