Vodacom Cancellation and ******** debit orders

Phoned Cancelation department to cancel both my cellphone contracts as my contracts were finished, they tried to smear off a "cheaper contract"on me because I was a loyal Customer... I declined and told them that I want both my contracts cancelled as I cant afford it due to personal reasons... they said they will cancel both the contracts back in September of this year.... October came and they deducted a smaller amount and i though this is due to a outstanding amount, but yet again I received a message that there was another debit order that went off... I tried to phone the contract cancellation department but it mentioned that both the phones are pre paid so please explain to me why there is money being debited from my account.