1. Officially Authorized Viettel Outlets: These are the most authentic destinations to get a SIM card. Find them in big shopping areas or malls. The staff can answer any question you have and will help assist in setting up your new SIM card.
2. Stores and Supermarkets: Many convenience stores or supermarkets such as Circle K and VinMart have SIM cards on sale. Just look out for displays or ask the staff if they have Viettel SIM cards.
3. Mobile Phone Shops: There are multiple mobile phone stores that sell SIM cards in Hanoi, especially in areas like the Old Quarter. These shops have a well-stocked selection of various SIM card types and accessories.