If a Dutch Bros. Coffee customer complained that you gave them incorrect change, what would you do?

"In my current position I have been trained to avoid this situation entirely by leaving the cash visible (out of the till and on the counter close to me) until I have provided the customer with their change. I will also confirm with the customer the bill type they have given me. For instance; if they hand me a 20 bill, I will say out loud 'from twenty?'. They will then say yes - confirming that we are both on the same page. These methods help me to avoid customer issues surrounding cash discrepancies."