Mobile phones often receive inexplicable text messages.

Some mobile phones have anti-theft tracking function. This function is triggered after the owner loses (or the thief replaces the SIM card), and this function will be notified by this short message and sent to the preset number. You may have a friend who used this mobile phone, set the anti-theft preset number as your phone number, and he changed his SIM card (or really lost it), thus activating the anti-theft function.