First, read the English article below.

Gather information that the support agent will need to verify your identity, such as your account number or billing address. Tell the support agent that someone is using your wireless connection. If your wireless modem/router came from your ISP, they can log into it and remove unauthorized users. If you think someone is using your password, ask your support agent to configure a new one at this time. Remember, passwords are case-sensitive. If it’s been a long time since your router has been updated, your support agent may also take care of this now. 

Now, please write a short abstract for it in Vietnamese. Abstract:
Chuẩn bị thông tin cho cuộc gọi. Giải thích vấn đề. Quyết định xem bạn có muốn đổi mật khẩu Wi-Fi hay không. Hỏi nhân viên hỗ trợ về thiết lập bảo mật thích hợp dành cho bạn.