Hi,
Initial call appears in the PANS-ATM at the following locations:
4.11.2 Contents of voice position reports
4.11.3 Radiotelephony procedures for air-ground voice communication channel changeover
7.3 INITIAL CALL TO AERODROME CONTROL TOWER
8.7.4.2 b)
12.2.4. a)
Cheers
aviator1945