Why can't some harassing messages be deleted ... mine is Xiaomi San.

Because harassment interception and other functions need to be controlled at the bottom of the system, they can only be realized after jailbreaking, and because these functions cannot be online in the appstore, the itunes version of the housekeeper has no system-level functions such as interception. If your iphone has escaped from prison, I suggest you search for "Tencent" on Cydia and find the installation of Pro, the mobile phone housekeeper of Tencent.