MiWay stole almost R5000 from my bank!

So I used to be insured with MiWay, but then they wanted to increase my excess with more than 300% for the second time. So I went to another insurer and cancelled my cover with them in May 2018. All was well it seemed my new insurer took their dues from my account and MiWay didn't, so everything is fine - NOT! Last week I received a call from a MiWay representative whilst at work but my signal was extremely poor, so he told me He'll call back after 4PM (he didn't). On Wednesday out of the blue I receive an email from MiWay with an insurance history letter. Then this morning I receive a SMS from my bank showing that R4 748.62 was deducted by MiWay? 5 Months after cancellation! This is nothing more than theft in my eyes.