Apple has issued a critical carrier update for Verizon iPhone 5 customers. The update resolves an issue where the handset may attach to a cellular network even though it is already connected to Wi-Fi.

To install this update:

  1. Tap Settings > General > About.
  2. Wait for the alert above to appear.
  3. Tap OK to install the update.
  4. Hold the Sleep/Wake button down until you see “slide to power off”.
  5. Slide to power off.
  6. 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.

Verizon customers are encourage to install this update as soon as possible. Without this update installed, the device may be using cellular data when it shouldn’t be.

Updated:

Since we first reported this issue, The New York Times has suggested the problem might also affect those using AT&T and Sprint iPhone 5 models.

Additionally, 9to5Mac is reporting that Verizon customers won’t be charged for any overages.

According to Torod Neptune, spokesperson for Verizon Wireless:

Under certain circumstances, iPhone 5 may use Verizon cellular data while the phone is connected to a Wi-Fi network. Apple has a fix that is being delivered to Verizon customers right on their iPhone 5. Verizon Wireless customers will not be charged for any unwarranted cellular data usage.”

We’ll keep you updated.