Not sure. But they provide a service called Caller ID that purports to identity callers but can be trivially spoofed by people scamming their customers. Moreover, caller ID used to actually work (IE couldn't be trivially spoofed), so customers might have a reasonable expectation that it still does work. It's the telco's responsibility to present accurate caller information to customers.
Caller ID could always be trivially spoofed. It's just that most scammers didn't previously bother to do it. Telcos currently have no legal responsibility to present accurate caller information to customers. That would require a new law.
