Explanation：When your monthly BASIC DATA plan reaches the upper limit of data, you can buy the EXTRA DATA plan. An EXTRA DATA plan has 10GB data for ￥10(10元), and it is valid for six months.

1. Please ensure your network account balance is enough to pay. You can refill your network account by machine according to the following steps. The machine is located near the stairs on the first floor of GengYun Building(FuCheng Rd. Campus).

2. Please use self-service website (https://self.btbu.edu.cn/) to add an EXTRA DATA plan. The specific steps show as follows.

Note: One EXTRA DATA plan has 10GB data for ￥10, and it is valid for six months. If you want to buy more data, please repeat steps show in last two illustrations.