Payments

I have given one month's notice to terminate my contract. A final figure for outstanding payments up to end of contract "Was Paid" as advised. SO NOTHING OWING. Then why have I been charged another month's payment - This is to be taken by ID on date stated ,and the payment I paid up to end of contract has been reduced by a month's payment. HOW CAN ID TAKE MORE MONEY when I will not owe anything as paid till termination. What is happening.