Ever get a phone call from a number that looks suspiciously like your own? This video explains them, and what you should do about them. (Jhaan Elker/The Washington Post)

I’d know her voice anywhere. “Rachel from Cardholder Services” has called me so many times over the years that I’ve got it memorized. The Federal Trade Commission tried to come between us in 2015 by fining Rachel $700,000, but Rachel kept calling. In fact, Rachel called me about a week ago. She sounded strange — not like the Rachel I know and loathe. Someone was impersonating Rachel. Yes, it’s true. “Rachel” is such a successful telemarketing personality that other robo-calling scammers are using her name.

Therein lies part of the problem: Robo-calls are hard to stop. Despite a diligent game of whack-a-mole — the FTC shut down three massive robo-calling rings between January and June of this year — Americans are still receiving an estimated 2.6 billion robo-calls a month. And robo-calls remain the No. 1 source of consumer complaints to the Federal Communications Commission. That, despite the fact that robo-calls have been illegal since 2009 (unless you have given the company permission to call you), and each illegal call is subject to a $16,000 fine. “Federal regulators have had a tough time enforcing the Do Not Call law to stop illegal robo-calls,” said George Slover of Consumers Union. “Even when the federal government has been able to identify robo-call scammers . . . it’s been difficult to actually recover the money.”

So why haven’t government and industry been able to put a stop to robo-calls? Lots of reasons. Cheap, easy technology allows scammers to place millions of calls from other countries, where they are beyond the reach of U.S. laws. Robo-callers fake, or “spoof,” the phone numbers from which they are calling, making them hard to track down. Phone companies worry that if they shut a known robo-calling number down, it may belong to an innocent customer. Plus, when they do block a number, robo-callers just switch to another. Here are some of the most common robo-calls:

Credit card rate reductions: This is what Rachel is peddling. She asks for as much as $1,000 in exchange for a credit card rate reduction that she never provides.

IRS back taxes: The scammer claims to be with the Internal Revenue Service and demands fees and fines. The Treasury Department says consumers have already lost $54 million to this scheme.

Auto extended warranties: The robo-caller pretends to be affiliated with your car manufacturer or dealer and sells bogus warranties. (The FTC sued one such scammer, and you may be due a refund.)

Pseudo Microsoft tech: The recorded message asks you to log on to your PC and hand over sensitive personal information.

Other common topics: These include home security systems, search engine optimization and medical alerts.

If anything, robo-calls are becoming more prevalent and more sophisticated. In their latest devilish innovation, robo-callers have been spoofing numbers in your own area code and prefix, which prompts far more people to pick up. They are also experimenting with artificial intelligence that allows the robot to hold a convincing conversation with you, as you can hear in a sample robo-call posted by Consumers Union in which the recipient tries to get the caller to admit she’s a robot.

While government and industry struggle to defeat the robots, there are several steps you can take to protect yourself:

Don’t answer. Simply don’t pick up calls from numbers you don’t know. You could even set your cellphone so that it doesn’t ring if the call is from an anonymous number or a number that’s not in your address book.

Don’t press buttons. Don’t try to opt out of robo-calls by using the call’s phone tree. “If you engage with the robo-caller in any way . . . it lets them know they’ve reached a live phone number,” explained Slover. “Your number is then added to a hot list.”

Don’t speak. If a robo-call asks you questions, don’t answer. Some robo-callers ask, “Can you hear me?” When you say yes, the scammers may use that to claim that you said yes to their product or service.

Get on the Do Not Call list. You should sign up for the National Do Not Call Registry, because then at least legitimate telemarketers won’t call you. Residents of some states have signed up far more than others.

Complain. If you receive a robo-call, the FTC asks that you file a complaint online or by calling 888-382-1222. The agency chooses which robo-callers to go after partly based on these complaints.

Sign the petition. Consumers Union is gathering signatures to pressure phone companies to be more aggressive about blocking robo-callers. “Nearly 750,000 consumers have joined our campaign and called on the top phone companies to offer free robo-call-blocking protection to their customers,” said Slover.

Protect your iPhone: For $1.99 a month, you can get the Nomorobo app, which won an FTC contest seeking robo-call slayers. It works by having your calls ring simultaneously on the company’s computers. (The company does not collect your information.) Once Nomorobo determines that a call is a robo-call, it hangs up for you — typically after one ring.

Protect your Android. Nomorobo will soon be available for Android phones, and you can sign up to be alerted when it’s ready. Meanwhile, CTIA, a trade group for the wireless communications industry, provides a list of robo-call-blocking apps for Android phones, some free, some for a fee.

Protect your landline. Consumer Reports had members test various landline call blockers, and testers preferred the Digitone Call Blocker, which has a one-time cost of $87 and silently thwarts robo-calls, with a red light letting you know that a call has just been blocked. Make sure this device is compatible with your phone before buying it.

Protect your VoIP. Nomorobo was first developed to protect VoIP phones, such as those provided by Verizon Fios and AT&T U-verse. This version of the service is free, and Nomorobo maintains a list of compatible VoIP phone services.