Charges!!!!

Please help me understand how I'm still receiving s statement stating I'm owing on my account when my contracted ended in July 2019 and I cancelled my contract after it ran its 2 year course and opted not to renew my contract. I also contacted the insurance department towards the end of July 2019 and cancelled the insurance as well. I was advised it was cancelled but that it takes 30 days to cancel therefore the insurance premium would still go off for Aug 2019. I was ok with that. On the 21 Aug 2019( which is the debit order date), the outstanding premium which was R27.42 was not taking out. I got worried, so I went into a vodacom Store in the Kwadukuza Mall in Stanger, and I advised them that the premium was not taking out.So the consultant went onto his computer and picked up the outstanding amount and advised I could pay it then and there. I paid the R28 on the 23 Aug 2019, thinking all would be fine now,expecting no other debits to be deducted. But I received statement 08/09/2019, stating I'm owing R55( of which includes the R28 that I paid, according to my calculations)..I cannot be going to and fro vodacom and customer care trying to sort out something which should not even be an issue. To avoid any legal action taken, please can someone contact me and explain what am I owing this amount for when i have paid up my debt.