The 4G services will be available for postpaid subscribers in the first week. SIM card change and update will be offered to all Viettel users from May 18. According to the group, the 4G SIM card, which has a capacity of 128 kb, is designed to fit all mobile phones in the market and is also applicable for 2G and 3G technologies. Viettel piloted the new technology in Vung Tau city in the southern province of Ba Ria- Vung Tau last December, with an average speed of between 40 and 80 Mb/s, seven times faster than that of the 3G technology. 4G is the fourth generation mobile data transferring technology with a maximum speed of up to 1-1.5 Gb/s, hundreds times faster than 3G.