Shopping online, making friends online, renting a car online, buying a second-hand house but not wanting to disclose your commonly used mobile phone number? The first step is to download the "Harmony" APP, and the second step is to choose a favorite minor number for yourself with the "Harmony" APP. The secondary number can independently switch the call and SMS functions, and can be controlled at any time without being harassed. On the basis of not changing cards and numbers, customers can add a secondary number by paying a monthly function fee of () yuan, which can be used online with the main number at the same time.