Need refund on the debit oder Urgently

I have a cell phone contract with Vodacom, so the this I make arancement to pay off the account and I do so very month with a debit order of an amount that I can afford, when I when in to my bank account on the 28 Aug 2020 Vodacom debit my account with 'n 4140 with out my consent of approval I have a monthly arrangement with them R500 per month I am still dowing a payment if not that I am not paying this is not wright, I have an arancement why are thy still taking all my fund out of my account