In this case it's an error in your favour. So I would not get too exited. Yet.
Personally I think direct debits are the work of the devil and should not be allowed. Given the option, I much prefer manual payments or standing orders.
I dislike the principle of "unspecified amounts on unspecified dates"
My hatred of them stems from many years ago when I paid for gas by DD. I cancelled the supplier and cancelled my DD. 2 months later, money went out of my account again, making me overdrawn, making me miss a mortgage payment because I was overdrawn, and costing me charges because I was overdrawn.
I told the bank I had cancelled it and it was their error. To which they replied WE cannot cancel a direct debit, only the debitor can.
It was only when I said in that case I'll close my account and move to a different bank that they finally agreed to reimburse the wrong DD, refund the overdraft fees, make the late mortgage payment (a standing order) , and write to my mortgage company explaining the late payment was due to a bank error.
If you do insist on using DD's my advice is mistakes WILL happen, so keep a large enough float in your account, so you can at least argue the mistakes without upsetting anybody else.