>not particularly difficult to intercept the call setup process from an AMPS phone and swipe its identification numbers, allowing you to basically steal someone else's cellular service. You can imagine that this was popular with certain criminals with a need for untraceable but convenient communications.

and Kevin Mitnick https://www.cnet.com/news/q-a-kevin-mitnick-from-ham-operato...

"I was cloning my cell phone to random subscribers and dialing into computers from the cell phone."