Revenue-desperate Vodacom billing after cancelation a shame

My last contract (1 of 3) ended in August 2017, called them to cancel. 8 months down the line they start billing me on the contract and threaten to take legal action against me. Where are the business ethics at Vodacom? I started with 3 contracts, I will never have any dealings with this dishonest giant again. Throughout the duration of these contracts I have had ridiculous billings against my accounts and they will blame anything just to escape responsibility. I guess the Court will decide.