What is the inexplicable number card issued by the mobile company?

Normal mobile companies send some, um, phone cards every year. These calling cards are actually a marketing tool. When you receive a calling card, you must open it. When you open it, it will have a monthly subscription. How much is the monthly service charge? He uses this marketing method to let you choose a calling card to spend.

Mobile card delivery is generally aimed at users who have handled mobile package activities, usually a main card with 2 or 3 supplementary cards. Calls between the main card and the supplementary card are free.