A Florida couple last week filed suit against Apple in a federal court, claiming that a new feature in iOS 9 caused them to exceed their wireless data cap, filings showed.

The plaintiffs asked a San Jose, Calif. federal judge to make the case a class action lawsuit, which if granted would allow other Americans to join in suing Apple.

In a complaint filed Oct. 23, William and Suzanne Phillips charged that Apple did not notify iPhone owners that the upgrade to iOS 9 -- which was released Sept. 16 -- included the Wi-Fi Assist feature. Wi-Fi Assist was designed to switch to a cellular connection if a local Wi-Fi signal was spotty or weak.

Wi-Fi Assist is enabled by default on iOS 9.

"Defendant failed to disclose to consumers that this automatic switch to cellular data caused by an activated Wi-Fi Assist (the default setting) may result in exceeding the data capacity allowed under their phone plans," the Phillips' lawsuit charged. "This is especially true as there is no warning or disclosure when the phone switches from Wi-Fi to cellular data."

When Wi-Fi Assist kicks in, the Wi-Fi icon in iOS 9's status bar -- at the top of the screen -- disappears, and only the icon for the cellular connection shows.

William and Suzanne Phillips said that they had exceeded their mobile plan's data allowance, but did not specify by how much or what overage fees they paid. Their lawsuit asked that Apple pay all members of the class action -- if the case was rated as such -- both actual and punitive damages. The suit alleged that Apple violated several laws, including ones banning false advertising and misrepresentation.

Wi-Fi Assist can be toggled off in the Settings > Cellular area of iOS 9.

Apple posted a support document explaining Wi-Fi Assist on Oct. 2, the lawsuit stated. The document included the line, "For most users, this should only be a small percentage higher than previous usage," referring to additional cellular data.

The couple's lawyers said that was too little, too late. "Defendant's corrective action, however, still downplays the possible data overcharges a user could incur," the lawsuit alleged. "Reasonable and average consumers use their iPhones for streaming of music, videos and running various applications -- all of which can use significant data. Defendant's corrective statement does not disclose any basis for its conclusion that an average consumer would not see much increase in cellular usage."

Wi-Fi Assist has had a mixed reception since its debut last month, with numerous blogs and media reports pointing out its double edge. iPhone users complained about the new feature on social media, while some took to Apple's support forum to ask if those reports were accurate.

The feature can be disabled in iOS 9 by going to Settings, tapping Cellular, then toggling Wi-Fi Assist near the bottom of the list.