Who take responsibility for disputed transactions

My handbag was ****** from the pick n pay in woodmead on the 24th October 2015, along with my cell phone in it. I immediately tried to get hold of the bank to put a stop on my card, when I eventually got help from the retail park security and was able to call the bank, there was already money withdrawn from my account, R3100, in 3 separate transactions. The lady at the call center confirmed that those were the only transactions on the account and that the card hard been stopped. On Monday morning when checking my account via internet banking i noticed that there was a further R4800 swiped from my account, when I called the bank i was told that the transactions occurred on the same Saturday and that they could not pick up any of these transactions as it happened over a weekend. A case of disputed transactions was opened and I waited for over 2 weeks to get feedback from the bank, I was then called only to be told that the dispute was rejected due to me not having called the bank in time to stop the card to avoid any further transactions and that because my did not look like it was cloned. My security pin had somehow been compromised, who would take responsibility for this? bad secur