Cancellation of Contract (Worst Service)

I went to the Centurion branch on 15/08/2015 where i filled in a cancellation form and was told the cancellation department would call me. I received a call from the retentions department offering me an upgrade which i declined due to their slow & bad service. I received an invoice in September whereby i called them & they said they would escalate the matter to cancellations again. 7 months later I'm still receiving invoices, i have called them more than 5 times & gave them this case no. ***4 and I'm not receiving any help, instead I'm told it will be escalated to Cancellation and unfortunately i can not speak to cancellations myself. This is the worst and most *********** people i have ever come across, all the respect i had for this company went down the drain. I'm not going to pay for services i cancelled & not utilizing and now this is reflecting on my credit record!!!<br>