What is Unicom's trumpet service?

On the basis of the existing mobile phone number (primary number), one or more (at most four) mobile phone numbers (secondary numbers) are added without changing the phone or card, so as to meet the needs of using different numbers to communicate with different people in voice, short messages and so on. In addition to supporting domestic voice and point-to-point short message functions, the minor number can also receive short messages starting with "106", but it cannot enable the data function and does not support value-added services.