Direct Debit Fraud

Just now as I was checking our bank account, I noticed a direct debit "first payment" had gone out. What?! We're just a small operation, and no one recalled setting up any direct debits. There were as many as five dodgy direct debits setup against our bank account. I know we can get our money back and all that, but these things shouldn't happen in the first place! Yes, our bank account number is public (otherwise how would people without cards donate?), so it's easy for somebody to put in our numbers in an application for mobile phones contract (as is the case here). So here's some questions for the bank then:

• How can we prevent it happening again?
• Shouldn't there be some simple checks done when a direct debit mandate is setup?
• Can't we be notified if a direct debit is setup?

I'm going into the branch on Monday (yes, apparently banks still have buildings and not just websites ;) ) and try to find answers to all these questions. Stay tuned.