Someone stole a short message with your mobile phone.

For this kind of person, no matter your classmates or friends, it is best to explicitly refuse him to use your mobile phone to do so. This kind of behavior will bring you trouble, big or small. If you want to express your refusal to him clearly, you can prepare an extra battery. It is possible to change a dead battery in advance when you are with him, and then change it to a live one after separation. Of course, it's troublesome, but after several times, he should understand that you are rejecting his behavior, but he didn't make it clear, so he can't say anything, and be careful not to use your mobile phone again.