Number match between received Calls or SMS and the Address book happens only
if some informations can be ignored, international prefix, trunk prefix - generally
don't saved because unnecessary to make a call. Those informations are extrapolated from a database using as access key the country code in the Sim-card, if you see the number and not the name may be those informations are wrong or missing. This application essentially replace the templates file with a corrected version.
You can find a list of supported countries here: http://www.spaziocellulare.com/ispazio/en/wp-content/uploads/2008/11/callerid-fix-22-more_info-10.pdf
You can learn how to install the CallerID Fix Collection by following this tutorial.