Standardbank VAF misplaced my lump sum deposit

I made a lump sum deposit to reduce my vehicle asset finance, after a week my deposit was still not reflected on my balance. When I called Standard bank, I am told I used the wrong reference number. I had used this reference number for the past 6 months with smaller top up payments and hadn’t experienced any issues. All payments were acknowledged, now that I made a large deposit, they suddenly can’t find my deposit and so cannot allocate my money towards my debt.