Apple issued a carrier update for the Verizon variant of the new iPhone 5 Sunday that claimed to fix a bug which, in some cases, caused the device to use the Verizon cellular data despite being connected to Wi-Fi network.

Apple’s support page for the fix said that the “carrier settings update resolves an issue in which, under certain circumstances, iPhone 5 may use Verizon cellular data while the phone is connected to a Wi-Fi network.”

Below are the instructions to install the update:

1. Tap Settings > General > About.

2. Wait for the following alert to appear:

3. Tap OK to install the update.

4. Hold the Sleep/Wake button down until you see "slide to power off".

6. Slide to power off.

7. After the device powers off, hold the Sleep/Wake button to turn your phone back on.

Note: To finish the installation of the update, your iPhone 5 must be turned off and then on again.

After your iPhone restarts, tap Settings > General > About, then scroll down to Carrier and verify that "Verizon 13.1" is displayed.

While the update has to be performed manually, it is delivered over-the-air (OTA). Although Apple described the update as an “important new carrier settings update,” the company didn’t provide many details on how and when these circumstances might occur, MacRumors reported.

9TO5Mac said that the issue in question could be “a carryover from the Wifi+Cellular feature that was in the betas of iOS 6 but was eliminated in the final version.”

The carrier update was preceded by a number of iPhone 5 users, who flooded Apple’s Support Communities webpage with complaints about the new handset racking up data charges while connected to Wi-Fi networks.

According to some users, the issue occurred due to some hardware problem with the iPhone 5. On the other hand, some other users believed that the issue was related to iOS 6.

“The first two days after I received my iPhone 5, I racked up 400MB of Cellular Data.  99% of the time I was using my phone, I was connected over WiFi.  So I ran a test on my own by watching a YouTube video over WiFi and then looking at my Cellular Data under the Usage menu.  Sure enough, it had went up by around 10MB,” wrote one user. “I called into Apple Support and asked them what was going on.  They thought that it might have been a problem with my phone or my house's WiFi connection.  After them walking me through a series of test and restores, the lady semi-acknowledged that it could be a problem with how their phone interacts with the new LTE network.”

“I think a "finicky" wifi in IOS 6 is the culprit here! I do not have a cell data plan (in fact, I even have it switched off from the network settings) and since upgrading to IOS6 internet over wifi has been extremely unstable, with the connection being constantly dropped,” said another user. “So I am guessing that if your wifi connection is also being intermittently dropped the phone will have to resort to the cell data to download whatever content.”

In another thread over at Apple’s Support Communities webpage, many users of older iPhones, especially the iPhone 4 and 4S, also raised complaints about excessive data use after upgrading their devices to the latest iOS 6.

According to Apple Insider, even if the new update is meant for Verizon customers, some thread posts did report similar issues with AT&T as well. However, the legitimacy of those claims has not yet been verified.

Will Verizon offer refunds to users affected by the glitch? Well, we’ll have to wait and see.