I have a somewhat related experience with DCB/premium SMS-es. I run a relatively small-but-not-trivial amount of IoT devices that communicate over GSM/2G. For that end I'm using a local GSM carriers "IoT SIM" cards/packages. A year or so ago we started noticing DCB/premium SMS charges on our account and that was super weird, as we know what our devices are capable and what not. First month it was a device or two, so there was a possibility someone stole our SIMs and is using them in regular phones or what. But next month, a lot more SIMs had these charges. We compiled our case, sent it to our contact at the carrier and the fees/charges were quickly dropped/refunded. All is well, it happens - weird but ok.

But a month or so ago we were tracking down some other issues and requested detailed connection logs for 2 of our SIM cards. And what do we find there? DCB/premium SMS charges. It looks like they are just filtering them out from our invoice and not charging them to us, but some backend system somewhere is still processing those fees.

So it seems like this whole DCB thingy is way more unregulated as one would think. Now I'm really interested how the charges even started appearing on our SIMs, why they did not resolve them at the source and how many people get their money stolen that way and they don't notice a few EUR here and there (fees were around 1eur in our case).

Interesting stuff.