cancelled my contract and still billed

In December 2014 I Immigrated out of South Africa. All my accounts with MTN had reached maturity according to MTN. I closed all but one immediately. I requested the last Data Contract to closed as of End of December, Latest End January. End January a debit order went off still, no account received. Emailed Customer services and They responded that my enquiry will be attended to. End of Feb another Debit order. I Send another email. End of March, End of April. In May I place a one month Block on the debit order. So Yesterday I finally get a mail from MTN that my accounts have been closed. This morning a debit order goes off from MTN for May and June! ***. 6 months additional billing after cancellation was requested after maturity of account? This is not acceptable!