Is there a charge for China Mobile's secondary number? What's the use?

China Mobile's "and multi-number" service: by adding up to three sub-numbers on the basis of customers' existing mobile phone numbers, it is not necessary to change phones or cards to meet the needs of customers for voice communication and short message communication with different people using different numbers; At the same time, there is no need to carry multiple mobile phones. Customers can set the on/off status of an auxiliary number in real time/regularly, so as to isolate the communication circle, protect privacy and not be disturbed. Every extension of 5 yuan/month. Due to the different business rules in different provinces, you can call local 10086 for consultation.