I got an iphone 14 pro max and I don’t know what carrier i can use

Return the phone for a refund.

Even if you knew the carrier that the phone was locked to, the carrier would not unlock the phone because their records indicate that the phone belongs to another person.

The phone has probably been "blacklisted", meaning that it cannot be used with any other carrier as well.

If you really want this phone, you will have to have the person that you bought the phone from contact the carrier that they were using to unlock the phone. Unfortunately, the person that you bought the phone from was probably not the owner. The phone was very likely stolen.

You will have to contact the original owner and ask them to have the carrier lock removed. They also should have gone thru the steps outlined here. If you cannot find the original owner or if they are unable/unwilling to unlock the phone, then you will not be able to use that iPhone.

Please read this article before purchasing any other used Apple devices:

The All Too Common SAD Reality of Buying … - Apple Community