Well, I have been using them for almost two years. For what it's worth, I'll post my review here.
I wouldn't refer to them as a scam. I can't speak to other services offering "the same for free" as I have only ever used Verizon (which no longer works great in my area) and AT&T. There are no other carriers providing adrequate coverage here (suburbs of NYC), so if I did use another cell company, it would ultamately just be "renting out" bandwidth on Verizon or AT&T. These companies like Fi, Mint, US Mobile, etc. end up with lower priority signal for their customers (compared with a direct AT&T customer for example). Hence the cheaper cost.
Enter Efani. With Efani I'm actually using AT&T as an AT&T customer but my customer service is done through Efani. This is the biggest benefit. Not dealing with AT&T, and instead dealing directly with a small boutique company customer service is wonderful. I pay less than I would at AT&T, for an equivalent plan. I can choose Verizon or AT&T very easily if the signal situation changes again or I move. There is nothing here to be scammed over. I'm getting AT&T cell service for slightly cheaper (admittedly they only have one plan - unlimited 5G).
As far as their marketing claims, I haven't seen them not living up to their promises, but then again I haven't had someone try to sim swap me. Regarding the 11-point security, I don't see why everyone is hung up on that. It is clearly explained online. It's not that big a deal and has nothing to do with encrypting the sim with digital code. It has to do with their secuirty practices regarding your personal info and account.
Overall, I don't see Efani as a scam at all. Just an alternative to Verizon or AT&T, focused on security in an area AT&T and Verizon have notabily failed in, over and over.
I am not paid by or endoresed by Efani. I don't care if you use them. I'm just giving my personal impression from me and my wife using them.