ERD50, I had a similar situation where my mortgage company paid both my, and somebody else's RE taxes from my account. It caused my account to be overdrawn big time. I had 6 months to bring it up to date and they increased my escrow by 2x. I think my new monthly payment was >3x my normal rate. That got my attention quick. They found the mistake and corrected it without issue. That was an internal accounting mistake though, not one regarding ACH fraud.
Like I mentioned earlier, I like paper billing. Getting a paper bill makes me open it and look at it. When my utility bill with auto pay (on a CC) comes due, I don't get a bill, I get an eMail or a text that the bill is available online for me to look at. I don't take the time out to look online. They don't say how much it is in the eMail. I don't get any kind of notification with my MC supplement bill, they just withdraw it from my account. I have to remember to write it in my checkbook. I do periodically balance my checkbook. I would see if something went wrong. I wonder how many of the younger generations still balance their bank accounts.