Chubb agr cancelled end June, put debit still thro

Our agreement was cancelled end Jun'15 with Chubb, today, 2 months later, they deducted R905 from our account by debit order. After speaking to 6 people at Chubb, I was notified that it is an outstanding invoice for a service entry from 12 FEBR 2014, 18 months back and still waiting for the supervisor to return my call. I will have to visit my bank to get records if it was paid or not, but my issue is: HOW CAN CHUBB DEDUCT MONEY IF AGREEMENT AND DEBIT ORDER WAS CANCELLED? They should have send me a detailed invoice to explain.