There isn't enough information to determine whether these accounts were properly "grandfathered" i.e. whether the customers were eligible for the accounts at the time they were opened, but the law changed after the fact.
As these are business accounts, Regulation DD does not apply. Even if it did, your bank can change its label for any class of accounts at will, so long as you list those accounts correctly on your call report.
Since July 21, 2011 financial institutions have been able to pay interest on demand deposits; i.e. you can open an interest bearing account for any type of customer you want. The change did not eliminate NOW accounts; it simply made it unnecessary to offer them.
I suggest you just revise the accounts so you don't have to tell this story again.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.