my account been bill without my knowledge

Im very disappointed in vodacom. There have been a migraine been done on my account and I have been billed for it. I haven't been notified of it or given any approval of it. When I reported it Vodacom didn't have the decency to call me back after i have to wait 15 minutes to report it. Im very disappointed in how they handle the matter and i realise that when i have to change my account i have to do security checks but when they went and make change on my account i have had no knowledge of. If the amount that was billed and the bank sent a it back i woukd have had a bad ITC report now vodacom have deducted extra money from me and i don't even get interested back on it .