Roaming SIM

A roaming SIM is a mobile phone SIM card that operates on more than one network within its home country. Roaming SIMs currently have two main applications, least cost call routing for roaming mobile calls and machine to machine. A roaming SIM is a mobile phone SIM card that operates on more than one network within its home country. Roaming SIMs currently have two main applications, least cost call routing for roaming mobile calls and machine to machine. Using a normal network locked SIM, travellers for instance, can use their own mobile phone (if it's enabled for roaming), in any country that has a roaming agreement with their home network, or for global networks like Vodafone, with another Vodafone OpCo. This manifests itself to most users when they receive a text message welcoming the traveller to a local network. However, once they return home their SIM will only work on the network with which they have a contract.