AT&T, Verizon and the GSMA are under investigation by the DoJ, under suspicion of making it harder for subscribers to seamlessly move between carriers, by locking new eSIM user identity technology to their networks.

Embedded Subscriber Identity Management -- or eSIM -- is supposed to be the latest alternative to the humble SIM card, which maintains the user's details on their phone, to be easily updated if the user decides to another carrier instead.

The New York Times first reported the U.S. Department of Justice has launched an anti-trust investigation into AT&T Inc. (NYSE: T), Verizon Communications Inc. (NYSE: VZ) and trade organization, the GSM Association (GSMA) . The DoJ is looking into potential collusion between the trio to hinder eSIM technology, the NY Times says, citing sources.

THe GSMA responded Monday, putting the development of the latest eSIM specification on hold, "pending the completion of an investigation by the United States Department of Justice." The GSMA says it is cooperating fully with the investigation.

The group said in a statement:

Carriers in the US have long locked subscriber phones to their network. Making it far more of a drag to switch carriers if you want to, and helping carriers prevent so-called user "churn."

In particular, eSIM technology has debuted in high-end phones and devices, such as the latest Apple iPhones or Google Pixel 2. This suggests that any lock on an eSIM would make it more difficult for some of an operator's more lucrative customers to move to another network.

— Dan Jones, Mobile Editor, Light Reading