Curfew at 18?

I'm in college, but I'm living at home this year to save some money. I've never been drunk, done drugs, or had , and this past semester I earned a 3.8 G.P.A. I am very responsible and I know what I want in life, therefore, I do not want to be promiscuous or do drugs. I have great friends who are responsible too. The ones who do drugs and/or have don't drag me into their problems because they respect my boundaries. My parents know all of this, so they should be reasonable when it comes to a curfew, right? Wrong. Sometimes my curfew is nine and sometimes it's eleven. They call me at least 2-3 times each time I go out, and I don't go out very often to avoid this. When I do go out, i usually just go to a friend's house to watch movies, or talk. I keep telling my parents to let me have a later curfew, but they reply with the cliche, "We trust you, just not the world" schpiel. Talking to them is difficult because they are so serious about this. What should I say to get a later curfew?