The reason a phone shows "SOS mode" is that it is not connected to its cellular network and can only make emergency calls. This can happen if the phone is in an area with no cellular network coverage (a coverage gap or dead zone), if there is a network outage from the cellular provider, if cellular data is disabled on the phone, or if there is a problem with the SIM card such as it being damaged, dirty, or improperly seated. In this mode, regular calls, texts, and data services are unavailable except calls to emergency services. To resolve a phone stuck in SOS mode, try moving to a different location to get better coverage, toggle cellular data off and on, restart your phone, remove and clean or reseat the SIM card, update carrier settings, or reset network settings. If the issue persists, contacting your cellular carrier or visiting a service center might be necessary as there could be a software glitch or a SIM card problem.