*****ing my money - DONT JOIN ONEPLAN

My husband was One Plan for about 7 months last year. We gave notice on 1 December 2014 stating that we would be leaving them end of December 2014 as we had joined Discovery Health again. Everything was fine and sorted out until I checked my bank statement yesterday and they had taken off R200? What the hell? How can they just do that and what for? We OWE NOTHING!!! Its been over 4 months till I left so what gives them the right to just debit my account as they please. They are *****ing, and if its happening to me how many other people are they doing the exact same thing to. I'm lucky I check my bank statement every day, what about those people who don't check there accounts regularly? ONE PLAN I WANT MY MONEY BACK OR YOU WILL BE GETTING A LAWYERS LETTER!!!