Online Banking Security

Good Day I have now spoken to 8 people and no one can help me, I consider FNB security of one time pin to be no use. I would expect a bank as big as FNB to be more security tight when it comes to purchase online. I attempted to purchase something online then change my mind before the OTP was entered and the amount still went off my account. Now I need to complete a refund form. Does that make sense? How could a purchase go through without a OTP? How can I now trust my money with FNB when there is such a risk. Please make contact with me. Regards Zahier