To start troubleshooting, let us first check the vendor's setup. It can be that you have the Multicurrency feature turned on and set the vendor to be paid with USD. Here's how to verify that:
Choose Expenses from the menu and click Suppliers.
Look for the vendor that had USD transactions and click the name.
At the upper-right, Edit.
Scroll down to the Supplier Information window and check the I pay the supplier with field.
If the vendor is set to the said currency, you'll want to start over by inactivating the vendor and recreate the bills. To make a vendor inactive, just click the Make inactive button in the Supplier Information window.
On the other hand, if the vendor isn't set up to a different currency, you can try performing a few browser troubleshooting steps. There are times that the regular browser stores cache file that can cause unusual behavior within the system.
Try using a private browser and check the Accounts Payable ledger report you pulled up. If the vendor shows the correct currency, you can switch back to the main browser and clear the cache. You'll also want to use other supported browsers to isolate these kinds of issues.
You can check out these links for more details in handling vendor transactions: