Don't bother 'phoning
I got one of these missives, as did my wife. I've tried calling the "helpline" (largely to vent my spleen rather than in the hope of any real action) only to be met with the usual robotic: "Thank you for calling Equifax, please choose from one of the following three options". Option 1 is the one you need if you are calling about their "data breach service" (nice name, sounds like a new product). Pressing that number reults in the repetition of the same message. As does pressing any other bloody number.
So they can't even get a fucking answer system robot to function correctly.