DONT CONTRACT TO IBURST THEY KEEP BILLING

My Contract term ended in November 2014. I notified IBurst in October that I would not be renewing my contract. In November I sent an official notification that I would not be renewing my contract. IBurst continued to process the debit order. I resent all comms of notice of non renewal in January and yet IBurst continued to Debit my account. Retentions called me in March and DEMANDED payment of the account that had been closed in November and NEVER used. I notified her that I would not be paying and she threatened me with a law suit. I resent the notification of non renewal to Retentions in March. Yes you guessed it THEY ARE STILL PROCESSING THE DEBIT ORDER EVERY MONTH.<br> Please can someone tell me how to get IBurst to pay attention and to STOP BILLING ME?