There are potentially several reasons why people might do these things while not conforming to goodfaith practices.
One of them is potentially cloning your voice, another is market manipulation, and logical inconsistencies tend to mean its AI driven which is what bad actors have embraced to mount cost effective attacks.
I call these attacks because these are resource drain attacks intended to impose cost and cause interference.
The market manipulation aspects are quite subtle, and what I'm about to discuss applies to just about any place communication where you receive a signal from a person,is used.
First, time is cost, and as a bad actor you can impose cost through deceit in open societies by stringing people along and other interference.
You can also saturate the environment so that business cannot be done. Jamming the medium.
The business pays their people to do business (labor), and when they are interacting with an AI the cost asymmetry is striking. You have real customers mixed in with fake bad actors. There is a conversion ratio for successful business transactions.
Now consider what happens when that same business is flooded with offers for the same thing, and instead of 1 in 100, its 1 in 10000. You have cost for each prospective candidate transaction that is sunk cost. Those costs scale until you cannot make profit, go out of business, and fail. Even if you ignore most, if you can't differentiate the good from the bad, there is no way to optimize cost effectively.
The same type of ratio is used for signal to noise ratios in communications. If you can't communicate because you cannot differentiate between the signal and the noise, no communication becomes possible. This is communications jamming, and interference.
Then there is also the targeted psychological effects of the manufactured distorted reflective appraisal you have of the situation. People use reflected appraisal in their judgments every day, these insights are often feelings about observations you've seen, and by and large they may not accurately reflect reality when manipulated for intent.
If all you see is that transactions have become impossible to make, and you can't judge actual demand, you may make mistakes and have to shut down, or sell your business for pennies. This concentrates the market, and some people are always the winners in this type of exchange (generally not you).
You may also do other things based upon those manufactured distortions, and few question whether that reflected appraisal that you get is actually correct. It largely happens underneath perception, and these entities are targeting that.
In many respects, its a form of torture and mental coercion often without you recognizing or knowing about it; few actually react correctly.
Joost Meerloo, Robert Lifton, and Robert Cialdini wrote books covering the subject matters involved.
Similar happenings are occurring in the jobs market with ghost jobs. By imposing cost tortuously, you create a market floor where new entities can't enter the market, and where some entities who are in the market, will go out of business. Its fairly identify who benefits the most in such arrangements.
Interference, Sabotage, and Sieving, Concentration, and brittle failures.
Who might stand to gain, large corporations in the same business sector, nation-states who are on a pre-war footing seeking to destabilize and demoralize prior to a hot war.
A collapse of the market is something nation states might try and induce, because that is in effect the collapse of the economy.
Chaos drives smaller companies dependent on debt, out of business to be gobbled up by large companies concentrating the market sector.
With regards to AI cloning, yes you should set up subtle challenge responses phrases and code words.
Code words are vulnerable to being recorded and reused. They are sticky because its hard to memorize, and not one-time use.
Challenge response phrasing may simply be part of the conversation, but with special meaning only between you and them.