There are two very different layers of call blocking, and the distinction matters here.
The options offered by Mudita Kompakt are device-level blocking options. The Kompakt can block hidden numbers, numbers not in Contacts, and individually listed numbers.
That explains an important limitation that Kompakt itself isn’t identifying spam. “Block unrecognised numbers” really means only accept numbers that are saved in Contacts. It doesn’t consult a spam-number database and decide, “this is probably a scammer.” Likewise, manually blocking +48 12 123 4567 only blocks that number; it doesn’t necessarily help if the spammer calls tomorrow from +48 12 123 4568.
So conceptually, the flow looks like this:
Caller → mobile network → Kompakt → Kompakt checks blocking rule → reject/allow
For a user like @YYZ , however, perhaps looking into network-level blocking, may actually be the better solution. In that case the flow becomes:
Caller → mobile network → carrier detects/blocks call → Kompakt never receives it
Depending on the carrier and country, network-side options can include spam/scam-call filtering, blocking anonymous/private callers, blocking specific categories of calls, anti-spam SMS filtering, or allowing customers to report numbers so the carrier can block or flag them across its network. Because this happens at the carrier level, it doesn’t matter whether the SIM is in a Kompakt, iPhone, Android phone, etc.
There is also a voicemail wrinkle. Device-level blocking does not necessarily control what happens upstream at the carrier. When Kompakt rejects a call, the network may interpret that rejection in a way that causes the call to go to voicemail, depending on the carrier’s conditional call-forwarding configuration. That’s why two Kompakt users on different networks can see different behavior even though they have the same blocking setting enabled.
There was a user on the FORUM, some time ago, who complained that they were getting tons of spam Voicemails and thought that somehow Mudita Kompakt could help with some better settings. However, it was more of a carrier issue because the call was never reaching Mudita Kompakt and ringing, but the carrier was forwarding it to voicemail. Unfortunately, Kompakt could not control that.