If someone’s cell phone is shut down and you pay the phone bill for him, then it turns off. How do you contact him? It’s urgent. Please help.

Are you sure he didn’t throw away the SIM card of his downed mobile phone? You can send a text message, just in case. Contact his friends. If you see him, help him and tell him that you have something to do with him. And asked if they want to change their number. If you change your number, I don’t need to say more. Or contact him through communication tools such as QQ. If you are really in a hurry, you can only go to the place where he often hangs out, or where you think he may be, or go downstairs to see if he is at home. If not, you can wait downstairs.