How do I know who is the carrier for my iPhone 14?

tap Settings > General > About > Carrier

Click on the link to read Apple's support article on how to unlock your iPhone for use with a different carrier. - How to unlock your iPhone for use with a different carrier - Apple Support - Only some carriers offer the ability to unlock iPhone for use on any carrier. Follow the instructions in this article to unlock your iPhone.

Click on this link for iPhone: Wireless carrier support and features in the USA and Canada - Wireless carrier support and features for iPhone in the United States and Canada - Apple Support - including a list of which ones offer unlocking.

Well, you pay your cellular bill each month to your carrier, so you should have a good idea who they are.

Contact your current carrier and ask them to remove the lock on the phone. Only the carrier can remove the lock. Apple is not involved.

Hopefully, you did not buy a phone from another person. Is that a possibility? If yes, you will have to ask them who the carrier might be.

Hello Kimmy-1!

It should show who your carrier is in: Settings > General > About.

Have a nice day, and good luck!

Return the phone for a refund. It is going to be useless to you until the previous owner pays off the phone.

The carrier is AT&T. They just told you that they will not do anything until the phone is paid off by the previous owner. Even if that is the case, AT&T still may not unlock the phone, as there are very likely other issues with the phone.

Sorry, but I think you have likely been scammed. Try to get your money back.

Contact ATT. Ask if they can give you the option of paying off the phone so they can then unlock it as a fully paid phone. However, it strikes me that even if they can it is possible the previous owner (who obviously was not aware of the things that needed to be done before giving you the phone) may have left other settings active. Those could prevent you from using the phone even if it was unlocked from the carrier. In particular if the previous owner did not remove the Find My setting this could end up locking you out of the device permanently, so I would first make sure the things in the link I provided had been done to see if it is even worth dealing with ATT. (Note that you are dealing with two different kinds of device locking.)