Phone shows no service after switching carriers or buying used

Symptoms

• New SIM shows 'No SIM' or 'Invalid SIM'
• Phone worked with old carrier but not new one
• Bought used and it never had service
• Carrier says the IMEI is blocked or blacklisted

Likely causes

• CommonPhone is locked to its original carrierA carrier-locked phone will reject SIM cards from other carriers until an unlock is requested and approved.
• CommonPhone reported lost, stolen, or with an unpaid balanceIf a phone is blacklisted (often called IMEI blocked) by a previous carrier, no carrier will activate it.
• PossibleSIM card size or type mismatchUsing the wrong physical SIM size or an eSIM-only phone without proper eSIM setup can look like a no-service issue.
• PossibleNew SIM not yet activated on the new carrier's accountA freshly issued SIM sometimes needs account-level activation before it works.
• Less commonPhone incompatible with the new carrier's network technologySome phones, especially older ones, may lack support for a specific carrier's network bands.

What to do

1. Check the phone's IMEI status (dial *#06# to find it) using your new carrier's or a third-party IMEI checker to confirm it isn't blacklisted.
2. Contact the original carrier to request an unlock if the phone is confirmed carrier-locked and fully paid off.
3. Confirm the new SIM card is the correct physical size or that eSIM setup was completed properly.
4. Check with the new carrier that the SIM/line has been fully activated on their system.
5. Restart the phone after inserting the new SIM.
6. If buying used, ask the seller for proof the phone isn't reported lost or stolen and has no outstanding balance.
7. Confirm your phone model supports the new carrier's required network bands.
8. If the IMEI comes back blacklisted, the phone generally cannot be activated on any carrier until the original issue (like an unpaid balance) is resolved by the prior owner.

When to call a pro

If the IMEI comes back blacklisted or the phone is locked and the prior owner can't be reached, a carrier or phone retailer can advise on options, though a blacklisted device usually cannot be reactivated.

Safety