retrieve my money from a ***** merchant

*** After I have made online purchase for a slimming product with BODIFITLEAN, in September 2014 I then realised the merchant is ********** as the amount selected was not what was deducted from my account. I called FNB to assist to retrieve the money but I was assistant in November. On the 21st January the same merchant BOBYFITLEAN accessed my account and deducted the same amount. Im now told by FNB that they can't help as the merchant told them I have an agreement with them which is not true. I want FNB to block and ensure that the merchant doesn't access my account in future. If the merchant truly have agreement with me they will contact me for their demand. If FNB CAN NOT HELP ME I SHOULD BE TOLD SO THAT I GET A BANK THAT WILL PUT MY INTEREST FIRST AND ENSURE MY MONEY IS SAFE AT ALL TIMES. IM VERY DISAPPOINTED with FNB services on this matter.