A little confused... I thought in your first post you said you had already closed your bank account and now you say its not closed but you want to get a hard debit block only. Maybe I misunderstood.
Anyway, be careful with the hard debit block and make sure nothing can get thru. If they can't get thru with an ach they will change the names and amounts and if that does'nt work they will try puting it thru as a check.
Have you talked with your bank already? I also bank at a smaller regional bank and when I went in and talked with them they set me up a new account right then and I made a list of all outstanding checks/debits and also deposits and they transferred everything to the new account. Several people have posted that is how their banks handled it as well.