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I suspect what he means by cloning is in the legal sense. Where law enforcement will "clone" a phone so they know who's calling, who's being called, and I presume have the ability to use the "cloned" phone to place calls from that number on a different handset.

At least I believe that's the definition of "cloned" he's looking for.

Of course with that said, I see no reason to answer the question. I might get chased away if I do!
Criminals can clone a sim and run up charges on other people's accounts. Pretty rare with GSM. I think it's rare in general these days. It was kind of an issue like 15 years ago but I feel like it's more of a social engineering type of thing to be victimized by that, these days. There was a video recently of a guy sitting in a minivan at a mall parking lot with probably 50 phones dangling from wires scanning for vulnerable phones of people walking by. So it does happen still and it's quite creepy.
 
I found a legit example of a Cloney Phone:
image.jpeg
 
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