unauthorized Debit orders on a cancelled contract!!!

I have a Vodacom modem contract that was cancelled months ago, yet I am still being charged! unauthorised debit orders? how can you guys even do that? it's absolutely terrible that you are taking money from people's accounts **********ly - I called 4 times and sent so many emails cancelling the same contract - and still, I get these debit orders on my account, the service is terrible I cannot keep calling your call centre- to cancel something that should have been cancelled months ago, stop wasting peoples time!