Carrier lock

A carrier-locked phone only accepts SIMs and eSIMs from the carrier that sold it — it must be unlocked before a travel eSIM will work.

A carrier lock (SIM lock) is a software restriction placed by the carrier that sold the phone, preventing it from using other networks' SIMs — including travel eSIMs. It is common on phones bought on installment plans.

A locked phone will usually refuse to install or activate a third-party eSIM profile, or install it but never connect. Checking the lock status before buying a travel eSIM avoids the most common "it doesn't work" scenario.

You can check under Settings (iPhone: General → About → Carrier Lock; Android varies) or by asking your carrier. Carriers must typically unlock phones that are fully paid off, on request.