Payflex frustration,uncalled for penalties

My payflex debit did not go off,to no fault of mine. Their excuse is that it did not go off to suspected manipulation which is utter nonsense. Then they charged me a penalty fee. I logged a enquiry and they just came back many days later to say that their t's and c's state that if a payment doesn't go off,they charge a fee. BUT...it's not my fault and my bank also states that the fault does not lie with them,so why must I pay a fine? There was ample money in my account. Terrible service from payflex,I will not be using them again *****sters.