
The Secret SIMs Used by Criminals to Spoof Any Number - fortran77
https://www.vice.com/en_us/article/n7w9pw/russian-sims-encrypted
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JPLeRouzic
_" operators of the SIM cards likely run their own Mobile Virtual Network
Operator (MVNO), which is essentially a telecom company piggy backing off of
the infrastructure of a more established network."_

This is certainly the trick, it may have little to do with the SIM card.

(personal opinion of a retired Telecom R&D engineer)

