I need help figuring out who my carrier is I just purchased an iPhone 13

It’s really easy to find out what your carrier is. All you have to do is go to a website like freecarrierlookup.com enter your area code and phone number prove that you are not a bot, and it will tell you your carrier. Hope this helps!!!

That will tell you the carrier that hosts your phone number, but not which carrier an iPhone is locked to.

When you buy a phone you get to chose your carrier from among all of the carriers that serve your location. If you bought the phone from Apple it will work with any carrier; if you bought it from anyone else it will be locked to a carrier, and you will have to use that carrier (at least initially). But the seller should tell you who the carrier is.