Unable to remove a customer from their system.

My wife left MTN as service provider because of the bad service at our local MTN store. She ported to Vodacom on 30 April 2015. In May she receives a sms from MTN, her account is overdue. We brought this to the attention of Chrystal Cupido whom works at the MTN store in Vredendal. At the end of May the debit order which is still active a month after the port, goes off against my wife's bank account. Again we bring this fact to the attention of Chrystal and on the same day reverse the money at the bank at our own cost. According to the bank the cancellation of the debit order must be done by MTN. The debit order also went off against my wife's account at the end of June. Again we brought this fact to the attention of Chrystal and her branch manager, Etienne Love. We reversed the transaction at the bank, again at our own cost and again attempted to cancel/stop the debit order at the bank, unfortunately with the same result. Today, 8 July 2015 my wife receives another sms indicating that her account is overdue. It seems that the debit order is still active 2 months after my wife left MTN as service provider!!!