Samsung Galaxy S26+ has no cellular service or data

The checks in more detail

If you use an eSIM, remember that it can be turned off or deleted by a reset, and a transfer to a new phone may need the carrier to issue a new profile. Check Settings, Connections, Mobile networks, Network mode and select the automatic option that includes 5G, since a phone left on a single band can lose service in some places. Select your carrier manually in Network operators to see whether the phone can find the network, and then switch back to automatic. If a call fails while data works, check Wi-Fi calling and VoLTE in Settings, Connections,

Wi-Fi calling and the mobile networks menu, because a carrier that needs VoLTE will drop calls from a phone with it off. A phone moved from another country may need the carrier's profile, so check that the carrier supports the phone. Update the software in Settings, Software update, since One UI updates carry modem fixes, and install carrier updates when offered. Remove the SIM tray, check that the SIM is seated and clean, and try the SIM in another phone, or another SIM in this one, to separate a SIM fault from a phone fault.

If the phone loses data only in one location, the network may be weak there, and a Wi-Fi calling setting helps. Reset network settings from Settings, General management, Reset, Reset mobile network settings, which clears carrier configuration and saved networks, and then try again. A phone that never finds a network with a known good SIM and after a reset may have a hardware fault, so run Samsung Members diagnostics and contact Samsung with the serial number; if the phone is on a carrier plan, the carrier can also check the line and the IMEI status. Avoid thick metal cases, which block signal.