Failure to finalise an Account debited even after cancellation of security contract

The area manager Amos had dealt with the cancellation of my Mother’s contract with Chubb, Ref ********** 9, back in October 2015 and by the look of things it was not effected immediately as it was supposed to according to the email he forwarded to his colleagues. My Mother’s bank account was debited twice/thrice by Chubb after the cancellation until she decided to go to the bank to stop the debit order. After a while she received notices that she should pay the outstanding amount of which fell after she had submitted the cancellation letter. She tried to resolve the matter and Chubb referred her account to debt collectors who keep sending her reminder messages for payment. Emails were sent to Chubb and Nudebt, whom I would believe are debt collectors on behalf of Chubb. Nudebt eventually responded by;

Sent:Thursday, February 15, 2018 2:49 PM To: Tshepiso Tlhareseng Subject: RE: Supporting documents - Ref ********** 9

Good day Tshepiso I did address the matter, the account has been placed on hold, it will be concluded by our query department."

After the response in February 2018, my mother continued to get SMS texts about the amount owed of R1114,53 and even today, 21 August 2018, she received the text.

Why is it taking so long to finalise this matter even after countless emails and live chats with NuDebt on this matter? This matter is long overdue and can it be FINALISED!!