T-Mobile IDs suspicious calls, “Scam Likely,” among other measures to reduce unsolicited calls their customers are getting. Here are ways you can avoid unwanted robocalls with the major wireless companies. USA TODAY

Perhaps it’s just a telemarketer. Maybe it’s an identity thief. It might even be a scam artist.

Either way, “Scam Likely” is probably not an old friend whose number you forgot that you saved. It’s your wireless carrier’s way of letting you know: Answer at your own risk.

To combat the seemingly rising epidemic of spam callers in the U.S., the nation’s four major wireless carriers have been trying out new methods to reduce the number of unsolicited calls Americans receive each day.

Some have built technology like spoofed call blockers into their networks, so there’s nothing you would even have to install. Others have taken a more passive approach, requiring you to download an app if you want to put a dent in the number of annoying calls you receive.

Regardless which carrier you have, you may have noticed that these unwanted calls just don’t seem to stop.

In fact, spam call blocking service YouMail reports that 4.7 billion robocalls blew up our phones in December 2018 alone, with the average person getting 14.3 unsolicited calls.

One of the reasons service providers haven’t been able to stop all these seemingly random phone calls is that scam call detection is inherently complex.

Determining that an incoming call is fake requires that massive data sets be analyzed in real time to spot anomalies. Some less sophisticated scam detection algorithms are easier for fraudsters to get by because they look at smaller data sets.

Also, the process of removing a valid caller’s number from a network’s scammer list can be slow, triggering false positives on legitimate numbers in the meantime.

“It takes a whole toolbox to fight the bad guys – blocking, labeling, customer education, industry traceback, enforcement, and Caller ID authentication,” said Andrew Morgan, a spokesman for AT&T in a statement emailed to USA TODAY.

Robocalls are still a plague. We tried out apps, phone features and the Do Not Call registry to stop them USA TODAY

The unwelcome calls epidemic is compounded since the two main agencies that are in charge of monitoring robocalls – the Federal Trade Commission (FTC) and the Federal Communications Commission (FCC) – halted operations due to the ongoing partial government shutdown. So, if you go to FTC’s National Do Not Call Registry to report a false number, you can’t. 

Here are the latest ways the four major wireless service providers are fighting against unwanted calls:

T-Mobile

In January 2018, T-Mobile implemented STIR and SHAKEN standards. STIR, or Secure Telephone Identity Revisited, is a call-certifying protocol. SHAKEN, or Signature-based Handling of Asserted information using tokens, verifies the caller’s right to use their phone numbers. In other words, these help to ensure they are calling from real, not faked, or spoofed, phone numbers.

Dubbed “Caller Verified,” this technology is now available through T-Mobile on the Galaxy Note9 and will be available on more smartphones later this year.

Whenever someone calls you, the nation’s third-largest wireless network checks that number against a database of known scam phone numbers. If the number matches a reported scammer, the Caller ID is flagged with “Scam Likely,” so you know to keep your guard up if you decide to answer.

T-Mobile, which has 79.7 million subscribers, offers a second feature called Scam Block that allows you to block these likely scammers before they can reach you. Scam Block works on all phones with Caller ID and is included with all postpaid plans at no additional charge.

“These advanced protection technologies put our customers in control,” said Mike Sievert, president and chief operating officer for T-Mobile, in a press release introducing the Scam Block feature.

The services have successfully flagged over 90 percent of scam calls, the company said in November 2018, which it says equates to over 1 billion unwanted calls.

T-Mobile and MetroPCS (which is owned by T-Mobile) first began rolling out the “Scam ID” features in 2017.  In November 2018, the mobile communications company further improved the unwanted calls service with protections against the increasingly common “Neighborhood Spoofing” – where scammers temporarily hijack a phone number to match the area code and three-digit prefix of the person they are targeting.

T-Mobile has a reporting website where callers can submit scam call corrections.

AT&T

Along with working to introduce customers to SHAKEN and STIR in 2019, the nation’s second-largest mobile network provides customers with Call Protect, a free app that blocks robocalls. As of mid-2018, the app blocked 365 million fraud calls and labeled over 429 million spam calls.

AT&T’s examines over a billion calls each day for patterns that may indicate robocallers, the company said in a statement.

For customers looking for even more protection, there’s AT&T Call Protect Plus, for $3.99 a month, which offers Enhanced Caller ID, Reverse Number Lookup and Custom Call Controls.

Sprint

“We are fully committed to deploying and implementing SHAKEN/STIR, and we are working vendors to begin testing various aspects of these protocols,” Sprint spokeswoman Lisa Belot told USATODAY.  “We believe the deployment of these technologies will be an important step in Sprint and the industry’s continuing work to eradicate the plague of illegal and unwanted robocalls.”

In the meantime, Sprint encourages customers to download Premium Caller ID, available on iOS and Android for $2.99 a month.

The robocall labeling and blocking service let you see who is calling, even if the caller is not in your contact list. Plus, you will be able to see the name of the caller

Verizon

The nation’s largest wireless carrier has a crowd-sourced list of nearly 300 million numbers that the company associates with spam and robot calls. The list is “literally growing and enhancing minute by minute,” said Joe Russo, senior vice president of network operations at Verizon.

As part of the company’s “full-on assault” against these unwanted calls, Verizon Wireless is rolling out a free spam-alerting and call-blocking tool to customers starting in March 2019.

For now, customers can download a $2.99 app called Call Filter that allows for blocking unwanted calls based on risk level.

“We use advanced analytics to really detect the good calls from the bad based on call behavior,” said Lauren Estrada, product manager of Call Filter. “To manage false positives, users can report that number back to us so that we can adjust that algorithm if necessary.”

If you are a Verizon Fios customer, you can register with Nomorobo, a free, third-party service that identifies known robocallers and telemarketers and stops your Fios Digital Voice home phone from ringing. Nomorobo will not work with Verizon’s Traditional copper voice service.