moneysavingexport.com the Martin Lewis organisation, has produce a comprehensive article entitled ’30+ ways to stop scams’ and I would encourage you to consider sharing it with your staff and volunteers, and using it as a checklist when reviewing your own policies and training plans.
You can read the article at https://www.moneysavingexpert.com/shopping/stop-scams/ and most of it applies just as well to organisations.
Also, and mainly because I mentioned it to a client in the last week, the NCSC has a very helpful Small Charity Guide which includes a great infographic that can be used as a posted on screen saver, and this can be downloaded from https://www.ncsc.gov.uk/collection/charity