Another day, another lawsuit against Apple regarding the iPhone. This time it's another complaint over the company's decision to lock the handset to only work with AT&T.

Attorney Damian Fernandez has filed a lawsuit in California, on behalf of his client, claiming that by locking the handset to the AT&T network, and re-imposing that lock with a recent software update, Apple has created an illegal monopoly.

Fernandez, in the court documents, said that Apple "punished" consumers and keeps them from "exercising their rights to unlock their iPhones."

Seems like a tough battle to prove users have a right to modify a product (and still claim it falls under warranty) as well as proving how a company can have an "illegal" monopoly over its own product. But so far, no news as to the court's reaction.

Fernandez is seeking national class action status, so that his suit can be expanded to cover all U.S. iPhone buyers. The legal firm handling the case has also set up a Website to encourage others to join the class action suit. The suit is seeking unspecified damages.