Additional Info
Typical case: MVNO offering 2 identities - one for home country, another one to decrease roaming costs. Dual-IMSI card.
In the home country, applet on the SIM card detects that home operators are available, thus uses home IMSI. In roaming, applet on SIM detects that roaming IMSI has to be activated.
Specifications
References
- https://www.gemalto.com/mobile/networks/roaming/dual-imsi
Definitions, acronyms and abbreviation
SIM Card - synonym of the universal integrated circuit card (UICC). The smart card used in mobile terminals in GSM and UMTS networks. The UICC ensures the integrity and security of all kinds of personal data.
IMSI - An international mobile subscriber identity. A unique number, usually fifteen digits, associated with Global System for Mobile Communications (GSM) and Universal Mobile Telecommunications System (UMTS) network mobile phone users. The IMSI is a unique number identifying a mobile subscriber. In the past IMSI was written on a SIM card during manufacturing process. Now there are possibilities of OTA updates, when IMSI and authentication parameters are provisioned over the air - for example eSIM or proprietary services by Gemalto.