Federal regulators are giving phone companies the right to block unwanted calls without getting customers' permission first. The Federal Communications Commission on Thursday voted to make robocall blocking the default stance with customers, in a move that could make call-blocking widespread.

Just one potential catch: While the federal agency expects phone companies to offer these tools for free, it doesn't require them to do so. Consumers can also "opt out" and ask their carrier not to block anything.

FCC Chairman Ajit Pai said he believes wireless carriers will have an incentive to offer these services at no cost. "These robocalls that are being placed on their own networks are a hassle and a cost for them to handle," Pai told the Associated Press.

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As the robocall problem has exploded to 5 billion a month -- or 15 calls per American monthly -- Congress is taking steps, too. The Senate has passed a bill that would require phone companies to do more, but it's not a cure-all. It still needs House approval, where Democrats in charge have their own bills that go further.

Even if all steps work, there are already concerns that scammers will figure out how to bypass them.

Phone scams have cost victims millions of dollars. And the aggravation isn't limited to scammers pretending to be from the IRS or Social Security. Call-blocker YouMail estimates that about a third of robocalls come from debt collectors and companies pitching cruises or insurance.

The robocall problem has exploded because cheap software makes it easy to make mass calls. Scammers don't care if you've added your number to the government's Do Not Call list.

Yet enforcement against illegal callers is negligible. Federal agencies have fined scammers hundreds of millions of dollars, but it's been difficult to collect, as many of the callers are overseas.