My parents recently read through my phone and found out i've had with my boyfriend?

My parents recently read through my phone and found out i've had with my boyfriend of more than a year (and who i have also known and been good friends with since i was 14). I will be 19 in august, and they still think that they can control my actions and how i think and feel. They loved my boyfriend until this happened, and now they are threatning that if I stay with him when I go to college in the fall, my relationship with them will be in jeopardy. They banned me from seeing him or talking to him for three weeks. I am allowed to talk to him over the phone now, but they still won't let me see him. I have been completely miserable this past month. I feel like they took away my best friend for a reason that has absolutely NOTHING to do with them. Am i wrong in thinking that they are completely insane?! I realize that i am not a fully grown adult, but i believe that i am old enough to decide what to do with my body, especially because we were very safe about it. I have gone along with their punishments and been very respectful by listening and taking into consideration what they have to say about it (even though they have had some rude and hurtful things to say about me and my boyfriend), but I don't know how much longer I can just put up with being treated like this. Any suggestions?