Belarus has three main GSM providers:MTS, Velcom, Life
They all provide no-contract GSM SIM cards and USB modems for Internet connection. In Belarus, cellular communications are extremely cheap and widely used. Each of these businesses operates a large number of shops in Minsk, Brest, and other regional cities. You will need your passport to buy a SIM card, but several rates are only accessible to people who have registered with the Belarusian authorities. However, a hotel stamp on the back of your immigration card in your passport is sufficient to register, and this is done regularly by hotels at check-in.