Facetiming internationally, Canada to USA?

So my friend lives in canada and has an Iphone 4s with Telus as its network with a basic 2gb data plan
I have the 4s with unlimited data on verizon
since we're not roaming on eaither our devices, can we both use 3g at the same time to facetime or will there be some international calling fee or some hidden fee?
I just want to make sure there are no hidden charges
I understand that it will use 3g on both of our plans

thank you so much for your help! Any info will help.

When you're using cellular phone data, there's no charge. It's just video-over-IP.

Which can get expensive as you may be using a lot of your data and could find yourself over your monthly limit which could cause you to have overage charges. But that would be the only charge. It's data and not a phone call. There are no more extra charges (apart from possible overage charges) than if you were to view a web page that is hosted in Australia.

And in the case of the 2G package, I'm not sure you've enough bandwidth to use it properly.

Your best bet is to find an Wi-Fi spot (either an open one or a private one such as your home) and use that instead. That way there are no data overage charges, you'll have good speed, and it'll be a better experience all around.