Unauthorised online purchases with the 0 online limit on my account

I would like to complain about Capitec. There are online purchases on my account withy account having no online limit on it but it went through. It had been going on for serveral times with small amounts until they deducted huge amount which raised my eyebrows. I went to the branch and was advised to change the card and query was logged. Today morning the same huge amount went off again after I have paid the R70 for the new card and with R30 limit for online purchases but the money is gone. Went to the branch again and when they called their head office I was advised that there is nothing they can do I need to contact those ppl deducting my money which I don't know. They even said they can't give me their details. The consultant at the branch was willing to assist me their head office don't care about the customers. R 1400 might not be a lot to them but to me it is a lot. Why was I advised to change the card when they knew that the money will still be deducted again. I don't do online purchases.