Oh dear, I've done this also. I would look up someones name in my received or dialed to see the last time that I talked to them, and for how long, then I don't know how, but the phone called the #. (lol) Did this a few time before my divorce, hung up immediately when I heard it ringing, and hoped that he wouldn't call me back.
If he did he was nasty anyway, so I had no problem saying I thought I wanted to talk to you, but realized I didn't.
I deleted him from my contacts. This way if I really wanted to call him, I would have to dial the phone, and I would cut my fingers off before I did that.