Someone used my SSN to open new credit lines, but my credit reports are frozen?

I found out the other day that someone has opened a new Kohls store card in my name, a wal mart card, a green dot bank account, and supposedly a chase bank account. I also got a letter in the mail that someone ordered $203 worth of shit from a mail order cheese company. My question is how is this possible if my credit reports have been frozen? I have verified they were still frozen. When I called equifax to question them on how this could’ve happened they denied the existence of the new accounts, but I have gotten letters in the mail and they have even shown up on Credit Karma. I am taking steps to close the fraudulent accounts and have set up a fraud alert but if it happened before with a freeze on my reports, what’s to stop it from happening again? And how did it happen in the first place? Is this on the fault of the credit bureaus?