MTN Don't Want to be Paid

I cancelled my bank cards at the end of November 2018 and earlier requested that MTN change my payment method over to debit order to which I received confirmation. I have now had multiple account smss from MTN stating that the card payments failed (of course because the cards don't exist) and the communications centre cannot seem to help after handing me over to the legal department (who have not yet managed to respond). I am trying to do the right thing and pay the accounts and yet MTN seems to be unable to help me pay them...?