Ask HN: Best Way to Stop Persistent Identity Thieves

About a month ago, my elderly parents lost their landline phone number in a sim swap attack. Since then, they have been battling with a scammer almost every day who has managed to gain access to their bank account, credit cards, and made fake IDs using their information. I helped freeze my parents' credit with all of the major credit reporting agencies, but the scammer managed to unfreeze that as well. I should note that the police have been useless here - a report was filed but nothing is being done.

Are there any stronger ways to harden my parents' accounts and frustrate the scammers? It's clear to me that they have quite a bit of information and persistence. Thanks!