Credit card

My credit card balance get deducted from savings ac on 28th as per instructions. On 29 and 30 Dec purchases were declined, was first told they had no instructions to deduct, and then that ac was blocked due to wrong pin no. ( I tapped, no pin no was used). They only deducted on 30th, and was charged R744 interest. Visited the bank, they found no reason for the delay, savings ac was in good standing, and no ac was blocked. I have been **** to, and sent from pillar to post.