FNB excess item fees a **** ,****med me over R1700 no explanation

Charged me R1710.00 on excess item on 4 rides less than R50 each for february,they dont explain how the amount came by all my money is gone and i need to use it, its all i had. According to their charges , excess items are honored by R55 each if transactions are below R50, the R155 if above R 50. So 4 transactions with 3 less than R50 should have been R165 then theR 52 one would be R155 bringing the total excess to R320 but they took R1710.no explanation and on my statement only those show.