How can I unlock iPhone which is carrier locked?

How to unlock your iPhone for use with a different carrier - Apple Support

Hopefully this will help you unlock the carrier!

By contacting the carrier it is locked to. Apple cannot do that and you will not be able to do it unless the carrier will unlock it for you. In many cases if you are not the current account holder of the service provider, they won't unlock the phone. You would have no idea in that case if the obligations of the account holder have been met to unlock the phone and the provider will not give you any information about that account due to privacy reasons if you are not the account owner.

Ask the wireless carrier involved if they'll unlock it. Nobody else can.

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