First Orion, an Arkansas company that provides caller ID and call blocking services, found that the volume of mobile scam calls has risen from 3.7% of total calls in 2017 to 29.2% in 2018. That number is likely to reach 44.6% by early 2019.

First Orion analyzed more than 34 billion calls made with partner T-Mobile USA (TMUS) and identified about 12% of them as scams. The 58 million T-Mobile subscribers see “Scam Likely” on the caller ID screen if the service determines a call fraudulent in nature.

During testimony to Congress in a hearing on robocalls and call spoofing this spring, First Orion EVP Scott Hambuchen said, “The fraudsters are very sophisticated, evolving their practices to avoid being labeled or blocked. As a result, we are in an arms race, not a marathon with a finish line, and will be in it until we make it unprofitable.” First Orion said it is deploying a new technology, “CallPrinting,” into a first-tier U.S. carrier network this fall to battle scam traffic.

The scammers are always trying to stay one step ahead, of course: phone number spoofing makes it appear that a number similar to your own is calling you, increasing the likelihood that you’ll pick up. Call-blocking apps only block known scam numbers, not legitimate numbers that are momentarily hijacked by scammers for spoof calls.

More than half of all complaints received by the Federal Communications Commission are about unwanted calls, the Washington Post reports. The FCC said Americans received about 2.4 billion unwanted automated calls each month in 2016. The FCC issued a $120 million fine earlier this year against a Florida man accused of making nearly 100 million automated calls offering people vacation deals.

Being on the do-not-call registry doesn’t help, because people who run scam businesses likely don’t give a fig about following regulations.