With the introduction of multi International Mobile Subscriber Identity (IMSI ) SIM cards, frequent travellers across several countries wouldn't have to pay hefty roaming charges and change their SIM cards in every country.
Multi IMSI SIM cards allow cell phone users to have multiple mobile numbers from different operators on a single SIM card.
http://timesofindia.indiatimes.com/...cell-phones-in-India/articleshow/12963646.cms