The traffic is used quickly. I suggest you try to download traffic monitoring software to monitor the usage of traffic in the package in real time. For example, Android phones can download netCounter Internet Manager through Google Market. Through software monitoring, you can find out which function uses traffic without your knowledge. For example, mobile phone viruses may transmit information in the background and cause traffic. Some commonly used software settings will also generate traffic, such as stock trading software. If it is set to refresh constantly, it may also generate traffic.