AT&T has confirmed in a statement that the new universal Apple SIM card in iPad Air 2 and iPad mini 3 becomes locked to the carrier after being activated on its network.

It appears AT&T might be the only carrier locking the SIM card after activation, as Apple confirms in a support document that “AT&T dedicates Apple SIM to their network only” with no mention of other carriers. The support document also confirms that “Sprint Stores will only carry iPads with legacy Sprint SIM cards (not Apple SIM cards).”

When Apple launched its iPad Air 2 earlier this month, one surprise was the company’s decision to include a new universal SIM in the cellular version of device. The Apple SIM, preinstalled in the iPads ordered through Apple’s online store and elsewhere, supports a number of carriers out of the box making it easier for users to sign up with the carrier of their choice. In the US it supports AT&T, Sprint, and T-Mobile (but not Verizon) and in the UK carrier EE.

Some thought the new Apple SIM, along with improved LTE support for a long list of carriers in a single model, would make it easier to switch between service providers on the fly. Apple even mentions “the flexibility to choose from a variety of short-term plans from select carriers” on its website. That’s not the case for AT&T, however, as users will have to change the SIM if moving the iPad to a new carrier (much the same as you had to do pre-Apple SIM). The device itself, however, is completely unlocked, the carrier told us.

Rumors that T-Mobile planned to lock the Apple SIM inside iPad Air 2 when purchased direct through its own channels were denied by the company.