Ask HN: atm cash-out antifraud - how to locate country of the phone in roaming?

I am developing anti fraud system for atm cash-outs outside of home country. I would like to make real time match of the region of atm cash out with the region of mobile roaming of the card owner.

I know that there're services to locate phones region that support api request for free or for small payment per request. Would appreciate references.