That's not really an advantage. If service providers and marketers were regulated reasonably, you wouldn't have to pay for receiving calls AND you could prevent telemarketers from calling you.
Here in Finland there's a number you can call to register your phone on a do-not-call list. It doesn't stop all callers I guess, but I have had no telemarketing calls since registering about a year ago, so it is pretty effective. I do get an SMS or two from my service provider every few months, but I'm not bothered enough to do something about it.
The UK has a similar system. It's pretty effective. the loophole is that telemarketers are not allowed to call, but market researchers are allowed to call.
Plus, in Australia at least, the calling party pays a premium to call the mobile phone (essentially charged at a long distance rate, to a separate 'mobile phone' area code). So in reality, spam callers self regulate anyway: they know what area codes are mobiles and they know that those area codes will cost them.
Here in Finland there's a number you can call to register your phone on a do-not-call list. It doesn't stop all callers I guess, but I have had no telemarketing calls since registering about a year ago, so it is pretty effective. I do get an SMS or two from my service provider every few months, but I'm not bothered enough to do something about it.