How do I unlock a sim-locked iPhone 12 Pro Max purchased from GCI Wireless?

The only people that can remove the SIM Lock on your iPhone is the carrier it is locked to. Apple cannot remove it. You purchased a SIM locked iPhone from an unknown seller, something you should not do. It is unlikely that the carrier will unlock it, probably because it has an unpaid balance or is under a contract. Try to contact the original seller of the iPhone for a refund or else it will stay locked and won’t be able to be used on any other carrier.

USC GCI Wireless is using the old trick of getting you off the phone by trying to blame the other guy.

Apple is not a carrier. Apple did not lock the phone. Apple cannot unlock the phone.

Only the carrier can lock the phone. Only the carrier can unlock the phone.

Call CCI back and ask for a senior support person. They will explain to you that you have been scammed.

If you bought the phone from someone, try to get your money back. Otherwise, I am sorry but you have a useless brick.

Apple won’t release a carrier lock. Only the carriers can request that lock be released.

Most carriers will only release the carrier lock when the terms of the contract are complete, or when otherwise required by law. Some carriers are reportedly willing to release the lock if the requester completes the terms of the cellular plan (pays). Others will only release the carrier lock for the person that they contracted with.

If the seller is gone, so no remediation and no refund, and if the carrier won’t accept payment to release the carrier lock, you bought a brick.

The All Too Common SAD Reality of Buying a used iPad/iPhone - Apple Community

Unfortunately, the person to whom you spoke gave you inaccurate information.

ONLY the locking carrier can remove a “Carrier Lock.” (They did after all underwrite at least some of the phone’s cost)

That said, ANY carrier generally will need an account owner’s info - if not active service - to verify that all contractural requirements for unlocking are met.

Sorry.