Double Deduction

On the 1st of December my debit for my monthly bill bounced. I made arrangements to have the bill paid on the 15th of December. I paid R488.07 (R476.67 of the original invoice and R11.40 admin fee for the returned debit order). On 2 January MTN billed me for R894.39, even though my account was for only R481.33 (R354.83 for number *** and R126.50 for number ***). Please explain what the additional R413.06 was for? When I phoned the call centre a while back I was being told that it was for an outstanding amount in 2014 (not 2015). I have checked the statements going back, and I paid every single month. I find it strange that MTN would wake up after more than a year and charge me for something in 2014. I went to one of the MTN stores, but they could not help me, so I resorted to e-mailing. I first mailed the query through on 27 Jan. I received a few responses from Tumelo asking for my statements. I then asked which payment they are saying i did not make (not prepared to mail 2 years statement through) and they could not tell me to which month this refers.<br> Not happy, because MTN is quick to cut off your service when payment is not received, but slow to reimburse.