A customer came back saying they were overcharged yesterday and only remembers the amount. How do I find the sale?

Open Find a sale on the POS. It searches by the receipt number, by the amount, or by the last four digits of a phone number if one was added to the sale. The sale shows every line, how it was paid and who took it. From there you can print it again, or start a refund, which a manager approves with their own four numbers. Reports → Shifts and the POS shows the same day shift by shift if you want the wider picture. The Staff, PINs and hours tab in the docs has a section on finding who served a customer.