ss7

There are dozen of companies providing services in this space. Many online credit card transactions are verified these days by doing a location lookup on the SS7 network, correlating the card holder phone location with the card holder current IP address (where the transaction is coming from). Just one example: https://www.google.com/patents/US20130030934 . SS7 is still the wild west, just like the Internet was in the early 90's or telecom was in 2600Hz era. Everything and anyone on the network is trusted blindly.