Security feature that keeps number from being ported to a new phone

If you’re asking whether AT&T has some kind of lock that prevents people who have access to your information from porting your number, the answer is no.

FYI Verizon does have what they call a port lock. But if someone gets access to your account to get your information, it's also extremely easy just to remove the port lock. Which makes it a lovely little virtue signal, but not an actual preventative measure.  I have been Verizon customers since August of 2019.

I'm also a member of their community although I don't participate very much. But I do read on a weekly basis where someone has been SIM swapped and ported out.

   If you have been following the news, there's an article that's been circulating widely, that employees are being offered $300 to SimSwap.  In other words cellular employees are being offered $ to defraud customers. 

Transactions can be tracked back. So if employee does this, they're probably going to lose their job because they will get caught. Every transaction is attached to an employee ID somewhere.  And if you decided to make this a sideline and you sim swap dozens of people for cash, you are definitely going to get caught.  

Carriers don't want their name besmirched. But it would make a whole lot more sense to make public when you catch people doing things like this so that other people will be discouraged from committing the same kind of fraud, knowing that they will get caught.

Somewhat related...A few years ago there was a news article where AT&T fired a whole bunch of people who were getting paid to provide unlock codes to third parties who were then selling those unlock codes to customers.