How does Unicom send SMS to open GPRS traffic?

Edit a short message with any character and send it to 100 10. 1 minute later, the system will reply you by SMS and list the standard charges. You can choose to open traffic packet 5. Accept the business, and then the system will reply to the SMS, including the monthly traffic item. After replying to the message according to the prompt, you can choose 5 yuan Package 30M or others.