For some customers the new technology now gives them a warning that comes up on their phone screens, such as “SCAM RISK” when a call comes in from an unverified source, giving the customer the option to pick up or ignore it.

Other steps taken by providers include blocking all calls from numbers that couldn’t possibly exist because of the combination of area code and prefix on its caller ID, and allowing customers to routinely block all calls with no caller ID, upon request.

The Federal Communications Commission set a deadline of June 30 for cellphone service providers to adopt caller ID verification, with a three-month informal grace period set to expire next week.

The five biggest cellphone providers — who together control 99 percent of the market —have adopted the new technology, with some exceptions for small portions of their networks, according to a new report by Massachusetts Public Interest Research Group, or MassPIRG.

But the report also found that many small- and mid-sized providers have not adopted the technology, particularly those who provide landline service. Some of them have an extension on compliance.

“We’re seeing strong progress, but there’s still a lot of work to be done to get the smaller providers on board,” said Deirdre Cummings, MassPIRG legislative director.

“The development of new technology, combined with the FCC requirement, really benefits consumers by significantly reducing the nuisance and danger of robocalls,” she said….

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