unlock old iphone that is not connected with a cell provider

If you forgot the passcode on your iPhone, or your iPhone is disabled or unavailable -

Click on the link for instructions on how to reset your passcode without a computer if you have iOS 15.2 or higher.

If you see an iPhone or iPad unavailable message or Security Lockout screen - Apple Support

Click on the link for instructions on how to reset your passcode using a computer.

If you forgot your iPhone passcode - Apple Support

Springtraining4life Said:

unlock old iphone that is not connected with a cell provider: Have an iphone that is 3-4 years old that is not in service and need to unlock the device to put it into service with a provider. I no longer remember the passcode on the Iphone."

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Getting a Carrier Lock Off:

Contact your Carrier:

You need to contact your Carrier, as they have locked it. Report back what they say.