BAD SERVICE, INVOICE RECEIVED AFTER CONVERTING TO PREPAID

I FINALLY MANAGED TO GET MY CONTRACT CANCELLED AND CONVERT TO PREPAID. I HOWEVER RECEIVED AN INVOICE DUE 31 JULY 2021 FOR R355.98 AFTER BEING ON PREPAID FOR A MONTH ALREADY. MY HUSBAND GETS HIS CONTRACT CANCELLED ON THE SAME DAY AS ME, AND HE GETS A CREDIT OF R6.99. HOW IS THIS POSSIBLE. I NEED VODACOM TO GET THIS SORTED ASAP AS THIS PAYMENT IS ON DEBITORDER. NEEDLESS TO SAY THAT IT IS HOPELESS TO PHONE TO TRY AND GET THIS SORTED. PLEASE CAN A CONSULTANT PHONE ME URGENTLY.