You have to send them the required notice. There is no exception if flood insurance is already in place.
The zone for rating purposes will be grandfathered providing the insurance was in place prior to the map change.
We add the following statement at the top of the notice:
You are being provided this notice due to requirements under Federal regulations.
We are in possession of the necessary flood insurance documentation for your loan renewal and no action is necessary on your part.
The opinions expressed are mine and they are not to be taken as legal advice.