Being billed even on a cancelled account

On the 19 of Jan 2015 my mom cancelled her telkom landline account because it was not working and the refence number was issued ref no *** and 3 months down the line statements was sent to my mom and telkom agents keep on phoning her demanding that she pays the account. then on the 5th of may 2015 I personally went to festival mall telkom office to find out they told she owes R442 because the cancellation done in witbank was incorrectly done. So i paid that outstanding amount of R442 and was issued with the cancellation ref no ***A. To this date my mother is still receiving statement on this cancelled account. I would like telkom to stop harassing my mom and honestly cancel this account.