He in the Navy

So my boyfriend went to the navy like two days ago and I’m curious. Could I send him a text message through the phone ? I was wondering because I don’t want to get him in trouble or the drill sergeant see it. I know they take their phones away but he been gone for two days so I don’t know what week they take their phones. I’m just trying to get my letters to him through the phone because he has not got the address to send to me so I can send the letters off. Can anybody let me know something ?