Double deductions

My sister retired at the end of April 2017. On 10 April 2017 I submitted a completed debit order form to change from a stop order to a debit order. The first debit order deduction was on 2 May 2017. a letter dated 11 July 2017 from Deidre Wolmarans Client Relations indicating that they have been unsuccessful in collecting premiums. I again forward the completed debit order form informing them that according to bank statements the premiums were deducted on 2 May 2017, 1 June 2017 and 3 July 2017. A sms was received indicated that the payment has been sorted out. However from August 2017 Metropolitan have made double deductions. I wrote to them on 3 October enquiring the reason for the double deductions, response received on 4 October 2017 indicating that the policy was owing for May- July 2017. Again I requested clarity for this as premiums have been deducted since May 2017. No response was received to my email dated, 4 October 2017, 11 October 2017 and 26 October 2017. I would like clarty what happened to the contributions that were deducted for May, June and July 2017 and why I have received no response to email. Seriously Metroplitan need to work on there customer service.