Bars without internet means the data path is misconfigured, usually the APN (your carrier's data gateway settings) or a stuck radio. Fixes take minutes.
- 1Confirm Mobile Data is on, and no data limit was hit (Settings → Network → SIM → Data usage/limit).
- 2Airplane mode 10 seconds on/off to force re-registration.
- 3Restart the phone.
- 4Check APN: Settings → Network → SIM → Access Point Names → 'Reset to default'.
- 5Roaming? Data roaming must be enabled to work abroad.
- 6Test the SIM in another phone / another SIM in yours to isolate.
- 7Reset network settings if all else fails.
Tip: If data died right after a plan change, the carrier may need to re-provision, one support call resolves it.