pfsense fritzbox?
Port forwarding set up, WAN rule set up, public IP specified on iPhone port 443, since no own domain with dyndsn exists yet, call via the public IP, unfortunately no access, access from inside the fritzbox works, what could be the problem,
either you didn’t get the configuration at the FB right or still didn’t get your PFsense right or simply you didn’t get your own public ipv4 address (key word DS-Lite, CGNAT)