Use this payload to change the device’s Access Point Name (APN) and cell network proxy settings. These settings define how the device connects to the carrier’s network. Change these settings only if instructed to do so by a carrier network expert. If these settings are incorrect, the device can’t access data using the cellular network. To undo a change to these settings, remove the profile from the device.
iOS supports APN user names and passwords of up to 64 characters.