Please help..guys recommended more but girls please you are welcome to help me too!?

how do you apologize to someone that u like (my bf).. if they are super super duper mad at u?..i don't see him at school(different schools) he doesn't answer my texts & when i call him he does not answer my phone calls or aether hangs up on me..its really messed up what i did i told him to go f*** himself for something so stupid!..how do you think i should say sorry?