I'm thinking & experiencing contrary to this- I've had cloned SIM happen twice, that I know of. I know the "who" part and believe me, 3 things come into play:
1.someone who portrays themselves as unknowledgeable with technology, but you witness them being extremely savy on something. If they can master _____, they can master something more challenging.
2. Motive- goes without explanation.
3.Opportunity- Ditto.
Sometimes these individuals who target someone, can be the same person we open our front door too, our lives and then it's too late. IMO- No one is to be trusted with anything digital of ours, any personal devices and nothing that stores information. Get a safety deposit box before you innocently hand over to a "trusted" friend something that may end up in someone else's hands for whatever reason.
Cloning/hacking is real, it does require some skill, it is very wrong,very damaging and if your phone has been cloned, clear the deck. You could go through a hundred devices and 100 of them cloned. Or you could save some frustration and take a long look at those who surround you, and noted points above. If nothing checks out, sleep on it. May just be your issues and accusing people without proof, is not cool. If you weren't cloned before, you may be now.
Bottom line, keep any of the things I listed safe! Worry smarter, not harder lol