banks incompetence cost me 3 extra bond installments

first FNB loses my deed of sale and now because of their incompetence i have to pay 3 extra bond installments totaling over R10k!!!! why cant FNB write off the amount that would not have been due had they NOT lost my paperwork? FNB, please take responsibility for messing up and waive the bond installments that WOULD NOT have been due had you not lost my documents. alternatively, i will contact the ombudsman.