You might have had your reasons for accusing him, but you did this not only once, but twice. In addition, he is allowed to talk to other girls, just as you are able to talk with other guys.
You are not ready to be in a relationship if you cannot get a grip on your insecurities, if you continue to strangle someone where they are not able to breathe without you jumping down their throat over some imagined slight.
Yes, he has the right to shut you down, cut off communication with you without warning because of how you treated him.
Use this experience to learn from your mistakes. Acknowledge what you did wrong. Write him a letter if you want, but don't mail it and don't give it to him. This letter is practice for you - to admit on paper what you've done wrong and how you can improve.
You may never get another chance with this guy. That's something that you have to face. You may never "get closure" with him. Life is like that sometimes. When you try to control someone else - as in he can't talk to other girls - when you try to strangle someone with your "love" - this can be the result.
If you learn something with this relationship, that's called maturity and you have learned a valuable life lesson.