Sometimes I just don’t know when a column is going to hit a nerve. But judging from the response to my May 19 piece, annoying telemarketing calls and robocalls rank high among the miserable irritants of everyday life.

Readers said the calls, particularly those that offer lower interest rates for credit cards and mortgages, are becoming more frequent, despite using every tool available to block them.

Reporting such calls to the Federal Trade Commission, as I suggested, was an exercise in frustration and futility, many readers told me.

“I have all four of my phone numbers on the Do Not Call Registry,” one reader, John Dingman, of Dallas, told me in an email. “When I report such calls, the FTC site thanks me and there is no other discernible response. The calls continue, perhaps from other companies, perhaps from the same companies with a new gambit and/or phone number. Who knows?”

Readers told me that the Do Not Call Registry seemed to work just fine at blocking calls when it began in 2003 and for several years after that. But the number of unwanted calls has steadily increased.

“I report them all diligently, but the calls continue to come and from the same organizations,” another reader, Kathleen Perry of San Diego, said in an email. “It raises the question, what happens to these complaints? Is there any action at all taken? I’ve received many more calls than I did a few years ago. Have telemarketing organizations discovered that this is toothless legislation?”

So I decided to take another bite of the apple and delve deeper into these complaints. William Maxson, a staff attorney in the division of marketing practices and manager of the FTC’s Do Not Call program, helped lead me through what I now understand is a multilayered maze.

First of all, legitimate organizations, in general, seem to obey the Do Not Call Registry. It’s the fraudulent calls that are becoming more numerous lately.

The reason?

“The technological advances in the past 18 months have allowed illegal dialers to increase the number of calls they can make and to spoof — that is, use fake caller IDs,” Maxson said.

No longer, then, should you think that these calls are coming from some boiler room filled with low-paid workers dialing and redialing with the same sales pitch.

With voice-over-Internet protocol, also known as VoIP, calls can be made cheaply from anywhere in the world, Maxson said. That is even more true with cloud-based VoIP, which makes such practices all the more decentralized.

Maxson laid out an example of how such calls might work so I would have a sense of the complexity.

A third-party company sets up software and technological capability that allows other companies to blast out millions of calls, Maxson said. Those are robodialers.

If the call asks you to press 1 and you do, you may be routed to a live person in a boiler room anywhere in the world. Those are called lead generators, whose sole purpose is to get the numbers of verified consumers to sell to telemarketers.

“They’re basically just fishing for people,” Maxson said.

The lead generators may ask, say, how many credit cards you have and what your average credit card debt is. At that point, two things may happen: Your name goes on a sheet that will be sold to telemarketers nationally or internationally, or you get transferred to someone — who also could be anywhere in the world — who will try to sell you something.

The pitches vary, but they usually promise lower credit card interest rates or mortgage rates or payment plans for debt avoidance. The practices are almost always frauds — promising services, getting your money and then failing to deliver. Or they ask for credit card information and make fraudulent charges.

In one recent case, the FTC shut down a company that sold worthless debt-reduction services and inferior extended auto-service warranties.

“We try to focus on the choke points, where there are a lot of bad actors,” Maxson said.

The ability of these callers to work anywhere, hide behind false numbers and elude enforcement may make the whole problem seem like an out-of-control Whac-a-Mole game. But Maxson said the FTC is trying to address the problem on a number of levels.

“We’re working with legitimate telemarketers and also with possible technological solutions that may assist us in tracking down calls more quickly or blocking them,” he said. “We’re aware this has become a bigger problem. These people are flouting the nation’s fraud laws as well as the Do Not Call Registry.”

Robocalls from “Rachel at card member services” seem in particular to be driving readers crazy. She’s one busy lady, as Blacky Bokich, a reader from Los Angeles, attests, saying he had received Rachel calls from 10 different numbers.

“Those Rachel calls — I would like to murder that person,” Bokich said. “It’s beyond frustrating.”