Terrible service at Telkom Mobile

I had a 2 year contract which ended May 2020. But they continue to debit my account even after I went to their shop to fill cancellation papers. No call center to assist or email to raise my grievance. I need help on how else should I cancel with because every month they debit, I reverse it the following month it's a bigger amount. Telkom's after sale customer service is terrible!!!!!!