Apple quietly rolls out a new online tool that lets ex-iPhone owners deregister their phone numbers with iMessage amidst a class-action lawsuit accusing Apple of failing to fix a technical glitch that prevented messages from being sent to the user's new device.

The tool, called Deregister iMessage, lets users unlink their phone number with their old iPhone even if they no longer have the old device. To deregister, users simply enter their phone number on the website. Apple will then send them a message containing a 6-digit confirmation code that they will enter so that Apple can deregister them.

Previously, the only way to deregister a phone number with an old iPhone requires physical ownership of the device, which is impossible for former iPhone owners who no longer have the device, as in when they handed it in to Apple's recycling program in exchange for a gift card or when they sold it as a second-hand device on eBay.

Users can still try out this method if they still have their iPhones. To deregister, they have to transfer their SIM card from the new Android, Windows Phone or BlackBerry smartphone to the old iPhone and turn it on. They then go to Settings where, under Messages, they simply turn iMessage off.

However, some users who opted for the older method report that it does not work all the time. People have taken to Reddit to complain that it took them a while of speaking with Apple Care representatives to have their phone numbers deregistered.

"Finally! I had to call in twice to deregister my mom's iPhone from iMessage because she doesn't have a data plan and wasn't receiving text messages," says one Reddit user who goes by the nickname mcax. "Both times I was on hold for 30 mins."

The Deregister iMessage tool is borne of a long-standing issue that many iPhone users who have switched over to other platforms have been complaining of. The users say their new smartphones are unable to receive messages from other iPhone users because the Apple system still recognizes their numbers as iPhone numbers, thus sending the messages to their old iPhones, which may no longer be around, instead of the smartphones they use.

In May, Apple acknowledged the problem, attributing it to a bug in the iMessage server, which it promised a fix for in an unidentified future update. This was after Adrienne Moore, a woman in California, filed a lawsuit against Apple which is now in class-action status, for her vanishing text messages.

"Apple tortiously (sic) interfered with the contract for cellular service between these putative class members and their cellular telephone carrier in that Apple's actions prevented the subscribers from receiving all of their text messages, as they were entitled to obtain through their cellular wireless service contracts," the lawsuit says [pdf].

Apple and the plaintiffs are set for a hearing on Nov. 13.