Abstract: Today, it’s almost true to say that we live in a mobile world. There are over 5 billion mobile connections world-wide, almost 4 connections for every 5 people on globe. When people’s are roam across the world they most important things is to carry is Mobile phone but when they don’t have valid subscription with network operator for roaming, communication with external world is affected. There is two option either he can subscribe for expensive Roaming & other way to buy the local SIM of corresponding roaming location (which may lead to carry multiple SIM). With this White paper we try to solve the issue of National / International Roaming without carrying multiple SIM card. With this concept a single SIM card may contain multiple International Mobile Subscriber Identity (IMSI) belongs to unique mobile phone number known as Mobile Station International Subscriber Directory Number (MSISDN) where MNO (or MVNO) are manage the MSISDN mapping with currently used IMSI at server end.