R1050 debit with no explanation

Im truly appauled by the service i received from Telkom and its staff members. I have a mobile contract with the service provider of which i took out in march . End of july was an extra R1050 debited from my account of which nobody can explain how i ended up running a bill of that amount while i hardly use the simcard in question. Im tried to get a hold of the manager of which i havent been able to get a hold of inorder to get an explanation. I want my money credited into my account!!!