Another Girlfriend Trouble Thread

[Vivalution]

Background: My girlfriend and I have been together a little over 1 year. We are still young though (21), so they possibility of us not seeing other people in the future is minute.

She has slept with the guy in question, and was in a quasi relationship with him before I whisked her away. He used to call her a lot, and I told her that wasn't cool with me, so she told him not to call her. In the last 9 months I have caught her talking to him a few times. Everytime this happens I tell her I don't appreciate her doing this, and if she had good reason to call him I would just appreciate her telling me. The guy lives in Washington by the way, where the girlfriend moved from.

Last night I am out getting pizza and beer with my friends, and my girlfriend sends me a text message that she would like to join us. Her cell phone is broken (she can only use some buttons, not including the answer button), so I call her house. Her mom answers, and I ask if my girlfriend is there. Her mom then asks if I am this guy, because my girlfriend told her he was going to be calling. I tell her no, it's Vivalution, have her call me when she gets home.

She called me later that night and told me the story. She is going to Washington later this week, and although she has a ride from the airport with her grandparents, she needs a ride back to the airport. I told her I wasn't upset about her calling him, I just wish she would of told me.

Now it is tomorrow morning, the beer has faded, and I am kind of upset. Several times, she has told me she understands I don't want her calling him, and she still does it. When she called this morning I told her, "oviously what I say or feel doesn't matter, you are going to do whatever you want to do."

Am I overreacting to the whole situation? Do I have the right to be upset that she talks to him in the first place?