Question: does iSync not support your mobile phone? try this.
So I did a little research. First I found this site http://blog.jayfields.com/2006/08/sync-your-samsung-phone-with-your-mac.html which links to this app http://homepage.mac.com/gaz/FileSharing13.html
After some experimenting, I discovered I can export in vCard 3.0 format, skip using the app, export a group of contacts to one file, and send it to the phone. Done. The address book on the phone contains one entry per name, each entry contains all of that person's numbers, and each number bears the correct icon for home, work, mobile, fax. Email addresses copy too.
This method of syncing is so easy I think nothing of deleting the entire address book from the phone, and uploading the whole contacts group again. Since that's what I've been doing, I don't know if uploading the contacts twice back-to-back would create duplicates. And as far as I know, there's no way to sync back from the phone.
But I don't care much about that. I'm fine recording a voice memo reminding me to make certain changes to an address book entry on the Mac and sync the whole thing again. Takes just a moment.
Perhaps in the future Samsung will be more SyncML and OpenSync friendly.
macbook pro, Mac OS X (10.5.8)