The companies will also offer many promotions to customers who buy 4G phones at their stores nationwide.
With these efforts, the two companies are targeting a total of 1.2 million Viettel 4G subscriptions from now to October.
Tran Kinh Doanh, general director of Mobile World, said 4G was a new trend that helps customers improve their working and studying capacity.
As of April, Mobile World had over 1,400 stores in 63 provinces and cities.
The stores have received 18 million customers monthly.
On average, about 700,000 mobile phones are sold monthly, with 50 per cent of them using 4G technology.
Last year, the company sold 3 million SIMs, and the figure is expected to increase to 5 million this year.
The Viettel SIM accounts for 42 per cent of the total number of SIMs sold by Mobile World.
Viettel is big network provider with 50 per cent of market share. The company provides 4G service throughout the country.