Nedbank Home Loan lost my money in my bond account. I now am told about a black file and how they have no recall seeing extra money being paid towards my bond

Nedbank Home loans. I am not impressed with Nedbank Home loans. Actually I'm in shock. From inception of my home loan, I have always paid a fixed instalment higher than my bond where the interest rate goes down. Paid extra towards my bond. Called them today to check how much is there. The consultant told me there's no fund or any extra money ever paid. I am now wondering what happened to all my money.I am now thinking should I have kept my money in my savings account than give it to Nedbank as they refuse to admit they have it and have no knowledge of it. They are now telling me about sending me a black file. Wow! ***