What did you order using your debit card recently? It would have been something ordered via the internet or you called to order.
IT IS PROBABLY RELATED TO THAT. IF you it was internet order - go back and read the terms and conditions on that site.
By the way - those free trial for the price of shipping and handling DO CHARGE YOU FOR THE PRODUCT. It is clearly stated the in terms and conditions. If you don't cancel within the trial time frame, they will charge you and THEY DO TELL YOU THIS ON THE WEBSITE!