My phone has automatically called  *44* twice now, does anybody know what this means? I heard my phone calling *44* while it was in my pocket.

Does anybody know what this code means, or do you know what process is calling this number?

I have a Samsung Galaxy S running Froyo 2.2.1 and I use a prepaid card.
It could be VAD. It stands for Voice Activated Dialing and is triggered by the service code *44*.

I'm not sure why it would do that all by its own without your interaction. An explanation could be that you are using a VAD supporting Bluetooth headset.