AT&T Locks Multi-Carrier iPad SIM, T-Mobile and Sprint Leave It Open
Apple public relations pointed Ars to a support FAQ that confirms the AT&T locking.
“Using Apple SIM, you can choose from different cellular carriers and their various programs. The data plans vary by carrier. For instance, in the United States, you can choose a domestic plan from either Sprint or T-Mobile and also pick an alternate plan from the other carrier as needed. When you choose AT&T on iPad Air 2 and iPad mini 3, AT&T dedicates Apple SIM to their network only,” Apple wrote. “If your Apple SIM becomes dedicated to a specific network and you want to choose from other carrier programs, you can purchase a new Apple SIM from an Apple Retail store.”
An Apple customer service representative told Ars that Apple SIMs are available for free at Apple retail stores. (UPDATE: I went to an Apple retail store and they charged me $5 for a new Apple SIM.)