Finance charges??? from where????? what are these???

Nedbank Credit card.they are charging me fees for transactions which is what is expected. but what the hell is Finance charges?????? every month i get this Finance charges Avg R600 every month. i never sign anything for this.... and what are these charges???? i am checking the credit card charges i cat find anything like this. i checked the when i signed for the credit card account it never mentioned anything like this. please reverse this charges, this is just *******...