Billed a closed account with notice

I called cartrack to close my account, with 20 days notice as required. They also assured me that it would not debit for August. But it was. I called for reversal, they said they would call me back after refusing to reverse. Still waiting for the call even today. This is more than 2 weeks ago. They have proof on their records of the conversations. I logged this complaint last week. No response yet