I just bought my 3G usb modem from Viettel today. 780,000 VND for the usb modem. 50,000 VND monthly charge, 65 VND per mb. You can recharge your account like any cell phone in Vietnam, no bills.  Initially I got up to 2.92 Mbps downloads with Speakeasy in the US. Not bad. Faster then wired.