Request to unlock iPhone 15 Pro Max

Used iPhone, as is usual for these questions?

If this was your iPhone and not a recent purchase, scroll down.

If this is a recent purchase, then at best, you bought the rest of the cellular plan, and a discussion with the carrier. At worst, you bought a brick. Carriers often won’t deal with a second-hand buyer.

Beat option? Contact the seller and request a refund. If the seller is still around. They too often disappear.

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

You likely have a brick, here.

If this was your iPhone and your cellular plan when it was under contract (unlikely, as you don’t know the carrier), then here is how to request an unlock:

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

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

You will need to contact the carrier to ask them to unlock the phone.

There is no check. You may be able to find carrier details in Settings at Cellular.

Also note, that cellular providers are under no obligation to unlock the phone if you are not their customer. You would have no idea if the obligations to unlock the phone have been met and the cellular provider will claim privacy reasons for not disclosing any details about the contract with the original owner.