Bad service from Netstar regarding cancellation

My 36 month contract is coming to an end and I contacted Netstar on 28 August to give my 30 days notice to cancel. I was informed by the consultant Kabelo to call or email after my August debit order went off. I sent an email on 6 September and received an auto response but nobody called or emailed. I then called again on 11 September and was told by the consultant that because I am calling on 11 September I will be charged an additional amount as they did not process my request on 28 August or 06 September. I asked to speak to a manager and have not received any callback thus far. I have even a loyal client and did contact them to cancel why must I be penalised for them not doing their job.