Spam robocalls suck and everyone hates them. They are a digitally-generated scourge on modern society, a small yet omnipresent annoyance met with universal derision. So AT&T’s wireless customers will likely be happy to see their carrier taking steps today to let customers block the unwanted calls — but there are a couple of big catches.

The good news first: the service, AT&T Call Protect, launches today. It’s a feature you can add through your AT&T accounts settings (myAT&T), or by downloading the Call Protect app directly.

The service includes automatic fraud blocking, which is basically a big ol’ blacklist. Numbers on it don’t reach you, but you can view the list of blocked calls whenever you want just in case you’re concerned you missed something legitimate. It also includes a suspected spam warning, which throws a flag up on any suspected spam source. And that’s not just “Lisa at card member services,” or IRS-impersonation scams, either; according to AT&T, it also includes “telemarketers, politicians, debt collectors, and more.”

In addition to the proactive services, Call Protect includes a blocking feature. You can block any number for 30 days, and continue to renew the blocks as they expire.

“Nuisance calls are an industry-wide problem that unfortunately affect many people,” AT&T SVP Jeff Bradley said in a statement. “We’ve listened to our customers and know they want a network that provides tools to proactively assist in blocking nuisance calls. AT&T Call Protect, along with others, will help put customers more in control of the calls they receive.”

Sounds great, right? Okay, now for the big catches.

For starters, the obvious: this is only for mobile phones, not landlines. (AT&T VoIP landline customers can already use Nomorobo, but traditional copper-wire customers cannot.) After that, the biggest catch? Call Protect only works when you have “HD Voice” enabled and are in a service area that supports it.

That’s AT&T’s internet-based (VoIP) wireless calling service; most wireless carriers have an equivalent. Customers using HD Voice on their phone don’t use a different app than their regular phone dialing process, but instead of being routed through the ordinary cellular voice network, HD Voice routes your call over the internet, like a Skype or FaceTime call without video.

AT&T specifies on their HD Voice promo page that the service is not available in all areas, and that prepaid customers can’t use it at all.

That means that when you’re out of range of an HD Voice service area (including international travel), you can’t get spam call warnings. Business/enterprise customers also aren’t eligible for Call Protect, because their employer is actually the account owner. So if you get your phone through work, you’re out of luck.

Also, call blocking has its limits: you can only block calls from known, identified numbers. So anything that comes through as “unavailable” or “private” can keep bothering you, without the Call Protect filters catching it.

Robocalls annoy everyone, but AT&T in particular has had a somewhat strained relationship with consumers desperate to escape endless robocalls in the past year.

In June, CEO Randall Stephenson claimed that the FCC was preventing him from putting robocall-blocking technology in place. The FCC, however, disagreed.

Later that month, AT&T customers around the country called the company to demand explanations for why they did not have access to robocall-blocking services, only to be met with all kinds of flimsy excuses.

By July, AT&T was admitting that robocalls are a huge problem for customers, but still wasn’t moving to do anything about it.

Stephenson, meanwhile, was named the head of the industry-led “Strike Force” tasked with ending the scourge of robocalls.

In October, that strike force introduced a plan that our colleagues down the hall at Consumers Union found half-baked at best.

“This latest plan is half a loaf, if that,” said Maureen Mahoney, policy analyst for Consumers Union, said at the time. “These efforts are aimed at getting better solutions in the future, but consumers need relief now. The phone companies should take immediate action by offering their customers the best call-blocking protection currently available.”

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