What product identifier is used for an iPhone when the CAS or IVR does not gather the appropriate information?

The IMEI, or International Mobile Equipment Identity, is a unique identifier assigned to mobile devices, including iPhones. It consists of 15 digits and can be used to identify the device on cellular networks. When the Customer Automated Service (CAS) or Interactive Voice Response (IVR) systems are unable to collect necessary information from the device, the IMEI serves as a reliable means to identify the specific iPhone, as it is tied to the device's hardware and is essential for network communications.

The other identifiers, such as MEID and ICCID, serve different purposes. MEID, or Mobile Equipment Identifier, is similar to IMEI but is used primarily in certain types of networks, such as CDMA. The ICCID, or Integrated Circuit Card Identifier, is associated with the SIM card in the device and is not specific to the phone itself. The serial number is more of a product identifier for warranty and repair processes but does not provide the same level of network-specific identification as the IMEI.