An ArcGIS Online organization with the Esri World Geocoder removed from the list of geocoding utility services defaults to using the Esri World Geocode service if a CSV is imported and the address does not match with the custom geocode service configured in the organization, resulting in credit charges.
Add the CSV via the Content page (Add > Add Item > From my computer). The issue is only reproducible when the CSV is added to Map Viewer (either through Add or by dragging and dropping).