DEBIT ORDER CHANGE NEVER DONE

I CHANGED MY DEBIT ORDER DATE ON 25 OCTOBER 2017 WITH WESBANK AND THEY STILL DEBIT MY ACCOUNT ON THE OLD DATES - I NOW PAY PENALTIES ON MY BANK ACCOUNT WHICH ALSO REFLECTS BADLY ON MY CREDIT RATING WHY CHANGE DEBIT ORDER DATES IF IT IS NOT DONE, I RECEIVED A CONFIRMATION THAT THE DATES WERE CHANGED, BUT THEY KEEP DEBITING ON THE WRONG DATES I CHANGED IT ON THEIR SELF SERVICE OPTION ON THEIR WEBSITE AND IT REMAINS UNCHANGED