Before making changes, print out what you have in case you make a mistake
If you want calls to Forward No Answer more than one step from your phone, you add CLS SFA to the place you FDN.
Caller --> Your
Phone --> 1st Place you FDN
--> 2nd Place you FDN
Dials You CLS FNA CLS FNA SFA Will ring forever
Link to this page: http://www.ghtrout.net/rdr/sfa.html