its pretty cool actually and i can start by saying its no scam or some stupid promo or anything. its very straight forward
first go to VoipBuster - Free Calls
and get an account. the going rate is 10euro for 4months of unlimited calling to about 30 countries. i use it at home with a linksys pap2 adapter just as you would get from vonage.
second, add your mobile phone number in the profile and then dial one of their access numbers. you will hear a message asking you what number you would like to call. enter it and press pound, you will then be connected.
on rogers i use a my5 plan so i have unlimited calling to 5 people and one of them just happens to be the access number voipbuster uses.
most of the time when calling throughout the usa and canada voipbuster doesn't charge anything, sometimes it will charge 1cent per minute but who cares that is deducted from the 10euro you already paid. i have come up to the end of the 4 months and the balance is still about 8euro. will just renew for another 4
its great for having at home as i need to make calls to europe and asia, free or 1cent per minute to major countries is nice. but the big thing is being able to call on the cell phone any time and not worry
here is a link to the mobile information : VoipBuster - Free Calls