Name the symptom
No service, failed calling, delayed messages and slow data need different questions. On a dual-SIM device, inspect which line is selected and whether one or both are affected.
Check the simple causes
Review official network status, restart the phone and briefly use flight mode. Confirm allowance and account restrictions. Follow model-specific instructions rather than guessing configuration from an unrelated device.
Preserve the recovery route
Do not begin by deleting an eSIM or erasing the handset. Network resets may remove Wi-Fi settings. Keep a backup and account verification available before any disruptive action, and tell support which tests were already tried.