use by mobile telecommunications subscribers of a mobile telephone or other device to make or to receive calls or to send or receive SMS messages or packet switched data communications on a visited ne, the ability to make and receive calls on a mobile telephone network other than the one with which the mobile is registered and using the same telephone number. In the global system for mobile communic, elektroonilise side teenus, millega mobiiltelefoniteenuse osutaja võimaldab oma kliendil kasutada mobiiltelefoniteenust teises mobiiltelefonivõrgus