Anybody recalls the device in the image below? Yup, that's the dial-up modem (internal). I come from a generation who started using Internet through one of these devices. I still remember the tone it would make & of course how could I forget the page loading speed. Ah! Nostalgia.
Let's come to the point. Back in those days to get online, you would need to dial up a number (provided by your ISP) with a specific username & password. During the same time Trojans abound the Internet that would create dialers which would make calls over international lines & you'd get hefty phone bills. The receiver would actually make money by directing those calls over premium rate numbers.
With the advent of ADSL modems, dial-up modems are gone from the Mauritian market. However, it seems like the phone call scams are back. Yesterday, an article appeared on L'Express newspaper alerting the public that phone calls from a Somalian number (starting with +252) might pester you. Upon answering you might get charged upto Rs 100.
Aren't incoming calls free?
Yup, that's what I've been thinking too. So far, I haven't met someone who actually has been victim of this scam. I can't say if really credit gets drained upon answering the call. If you call back, I'm sure it would.
How do these scammers make money?
The same principle as the dialers apply here. Once you dial back the (Somalian) number you're actually ringing a premium rate number. Say, something like the local "audiotex" services that usually charge Rs 3/minute. However, in the case of Somalian numbers you could be charged upto Rs 100/min.
As for now, I don't think mobile network operators can do anything about it, legally speaking. The best shot will be blocking the numbers on your device.
It looks like some PABX systems can be triggered to automatically call back such numbers (^^,) ...