It looks like even though SMS messages can't be sent free of charge, SMS spam and fraud seem to be on the increase and I suspect a significant part of the population may be vulnerable to be tricked into calling premium numbers that way.
When I recently talked to a somewhat elderly person I was told a story about an SMS the person had received which looked like it was sent by a popular parcel service company. The message said that they had tried to deliver a parcel but found nobody at home to receive it. The message then requested the person to dial the number in the SMS message (or click on it) to call the parcel service to arrange for another delivery. The number, of course was a premium number but not all people recognize such numbers, especially in countries that don't use 0900 or other well known codes for such numbers.
In this particular case, no damage was done because when the person tried to call the number it was already deactivated. It looks like the fraud was discovered and shut down.
What is really bad about the whole thing is that even after I explained that the SMS message was a scam to trick people into calling premium numbers, the person still insisted that the message has come from the parcel delivery service. I am not sure my explanation has sunk in 🙁 And the person I was talking to was not dumb, just not born in the mobile age…
Difficult one to solve I fear. The same applies for emails and even to some extent post. It is difficult to make electronic trust easy to use.