Rain is very unprofessional

Good day, we have cancelled our Rain services 16 July. Rain have deducted R999 end of July for the use of August which we did not use because it was cancelled and we already installed new WIFI providers. When I phoned them they assured me that this was cancelled and even sent me the cancellation. Now end of August they deducted another R999 this is very upsetting and they just refuse to refund.