No authority to debit

Many moons ago I had a contract with MTN that did not have a happy ending, however parts of my query were addressed earlier on this year. But I have picked up a debit order going off my account of R64 with ref number APL ********** 947/24HRW4884, I called my bank to investigate and they gave numbers of a company called Constantia Insurance, then Princess from there gave me a number for 24hour mobility. Erica at 24HM told me that in was insurance for a Sony Ericson X10 Mini that I had in 2010, I informed her that I had cancelled my contract with MTN ages ago and who gave them the authority to debit my account for a cell phone that doesn’t exist in the world any more. This is ********* and will be escalated to the ombudsman. This must be refunded and my account is not your play ground.