MTN trying to get rich

my contract with MTN ended last year of which at the time I called MTN and cancelled my contract, After a few months they started debiting my bank account and i had to keep going and reversing the transactions. after a number of attempts to get feedback from MTN and after Experian tried to get feedback from them all has failed. now i find out that they again listed me on ITC and still no one from their accounts department has called me to advise why I owe them and for what.