I Did It For My Sibling

My big sister always had it easy. Born first, she got all the cool clothes and gadgets before I did. And let's not forget about her bedroom, which was twice as large as mine. But things changed when we turned 15. She started dating this older guy who looked more like a grown-up than our classmates. He had money too; they'd go out for fancy dinners and movies that I couldn't afford or even see until much later in life. I was jealous, so jealous it hurt. And then one day, the opportunity presented itself. The guy dropped his phone at school without noticing. I picked it up, looked around to make sure no one else had seen, and decided to peek inside. First thing? Lots of photos of him and my sister on vacation in some fancy place with a beach and pool. No way was that fair. So, I took the phone and went home where I called his number pretending to be my sister saying she wouldn't pick up any more calls from him because she needed space for school and stuff. And guess what? He broke it off right away! At first, everyone thought my sister did it herself, but later on at a party, someone saw me with the guy's phone. That was enough to get the story out that I'd played a prank, not her. Now, I'm proud of myself for taking action and making things fair for once in our life. Was I an asshole? Maybe. But it felt right at the time. So here's my question: Am I really the asshole for doing this, or am I just someone who stood up to make sure we both got treated equally?