So you pay to buy sim cards instead of to pay to enhance your account?
That sounds stupid.
So if you have 20 phone numbers, 20 different emails and 20 listings with same topic, how do you know it's same user and not 20 different users? what if all 20 listings got paid premium/highlight feature? What if each of listing will use different set of images?
So, once again, the scope of such plugin is to prevent users to post for free listings which we were allowed to be free only for a month per category. To encourage users to chose your site from tones of other competition we want to have this feature and to give any user the opportunity to post free for a month(or whatever we decide) and then to automatically enforce payment for new(or same) listings he wants to post in same category. So, after grace period passed, he can post same listing or new listings in same categories using our free option if he use different identity/user-account. We want to identify the both situations and to not allow the user bypass the payment by tricking the rule and posting always as "first month free listing".
"So you pay to buy sim cards instead of to pay to enhance your account?"
Enhancing the account makes sense when you are selling daily, as a business/job but not the case of(thousands) users who sells only one time, a single property(for example) and it takes 6 month(or even more) to sell it. He doesn't want to pay every month.
OLX has this function(they're using AI)