Vodacom at it again!!

I was de*****ed by Vodacom Rosebank in March17 when I attempted to end my contract,they instead upgraded. I went up and down to get the whole thing sorted. Eventually vodacom admitted fault and paid back some of the money they had debited from me. A year later, I am contacted by debt collectors that I owe vodacom. No one can explain why n vodacom call centres are a nightmare to access. As far as I know, I stopped doing business with vodacom in 2017 after they paid me back!!