I just find out there is a VOIP app already - Truphone. Don't know how god and reliable is this but worth a try?

Also another question.

Don't know why it takes forever to sync when I enable "contacts" to be sync (Outlook - on my laptop). It seems it is trying to resync everytime? I thought it will only sync if I added something new?

I have switched it off at the moment. Actually I have switched off all the Outlook stuff sync at the moment.