Okay, both * and # do have meanings in certain areas (and still are), but outside of US military (and this is actually already historical, nowadays priority is linked to the specific handset and some lines are always reserved) Priority A (Flash Override (FO), for Presidential use), Priority B (Flash (F), for breaking events), Priority C (Immediate (I), for urgent but non-life and security-threatening events), and Priority D (Priority (P), officers versus ordinary soldiers) are never used because a) due to the possibility of confusion with numbers like 1-800-ALPHABET and b) AT&T have invented Priority signals specifically for US military's use (although standardised now internationally for some reason: https://www.itu.int/rec/T-REC-Q.955.3-199303-I/e).