web site continuess to charge every month for one time service

I let my son use my debit card on a web site for looking up things on people now I can not get it stopped from charging my bank account once a month for over a year. In Jan 2007 my son use the Net Decective net to find out some information on someone. The web page reads threes years for one price of 29.00> well they are still charging and I have tried several ways and times to get it sopped. Can you help me Please.