What happens if someone tries to do an electronic withdrawal on a closed bank acct.?

I moved to a new city and closed my bank account. I had a few things that were taken out electronically and I've cancelled all of them, but I know from past experience that sometimes that doesn't always work and companies claim they never received the order to cancel the electronic withdrawal and keep doing them. Maybe I'm just being pessimistic, but I always expect the worst when it comes to this kind of stuff. I know I don't have any uncashed checks out, but what happens if a company tries to make an electronic withdrawal from my account after the account is closed? Will it just not go through or will I be penalized in some way for this (penalized by the bank, not the company trying to withdrawal money)?