Supersonic not responding to Cancellation of Service

I decided to change fibre ISP provider and requested Supersonic via email to cancel my subscription on the 14th of August. I received an automated response from Supersonic to acknowledge receipt of my cancellation request. A Supersonic retention agent phoned me at the beginning of September to confirm that Supersonic will release my fibre line with Vumatel on 30 Sept. This did not happen and my bank account was again debited in Oct with the monthly fees. Despite more emails, no response from Supersonic. Impossible to phone these guys at Supersonic unless you want to talk to Sales.