MTN IS DEDUCTING MONEY FROM MY ACCOUNT AND I DONT KNOW WHY

I AM SO ANGRY WITH MTN, I CLOSED OF MY CONTRACT WHICH WAS DEDUCTING 190 PER MONTH BUT LAST MONTH THEY DEBITED R3000 FROM MY ACCOUNT WHICH I HAD TO REVERSE AND THEN THEY SENT A TEXT THAT I SUDDENLY OWE THEM 4000 THIS MONTH THEY SENT ANOTHER TEXT THAT THEY WANT ME TO PAY 2500 . MTN IS THE WORST