I'm being blacklisted for an error by employee in Bloemfontein Waterfront Mall

I opened a contract with vodacom in Bloemfontein at Waterfront. They had a promotion on data last year around October. I was assisted by Reggie. I told him I want sim and the router but he only did the simcard. When I queried about it he said I should not worry he will give me his own at home as he could not add it to the deal and will deliver it to my address. Which he never did the Sunday morning until I went in store. He said he forgot and will cancel the deal. Month end they deducted an amount over R400 and I went to him to ask why they deducted he said its an error I should just reverse it at the bank and I did. Till today vodacom still sends me account and now is threatening to send me to blacklist me. I'm not sure how they do things at this company.