Following Apple’s release of iPhone OS 3.1.2, AT&T has released a carrier settings update for its U.S. iPhone customers. Listed as AT&T 5.6, it is unclear what improvements the new settings file may offer; the last carrier settings update activated MMS service for U.S. iPhone customers. AT&T announced earlier this week that it will now allow VoIP iPhone applications to operate over its 3G network, but it is unknown whether this new…
