Money debited from my account for no reason

First of all I want to say I am extremely furious, I have never been so angry in my entire life. I had 2 contracts with cell c, one of them ran til the expiry month and the other I paid it off in October and asked them to cancel it. I was told to pay R2428.71 and I did just that. A day or two later I received a confirmation SMS from cell c stating they have received the payment, I called customer service to double check and to cancel because I wanted to port out. I was told both my contacts were canceled. So I am no longer with cell c, their service is as pathetic as their network coverage. So this morning, December 1st, cell c debited R561. 71 from my bank account. First of all I want to know who gave them permission to ***** money from my account, I consider this as *****. I am no longer with them so why keep my banking details on their system. Secondly I demand a refund I have an account that I'm supposed to pay for with the money so now my financial commitment has to be on hold because of one *********** company who's employees don't even know what they are doing. I called customer care this morning wanting to request for a refund the consultant told me she cannot help me because my account is deactivated, she transferred me to the legal department who too couldn't help me because it wasn't a legal matter. So I don't know who to reach out too. I think it's ironic that they can't access my deactivated account when they can do as they please in my bank account. I angry, I'm hurt and i want my hard earned money back. I cannot believe that such a big company is ripping me off like this and no one can help me