So i've heard of this Viber on android which is free international calls, but I want to make sure that there's no catches.

My phone and the person I want to contact both have unlimited internet, both with Wifi and 3G.

We are both T-Mobile too.

Just want to know what data plan is as Viber says this:
'Go ahead and start calling and texting. It's free* and it works great!
*Calls use your data plan'

And also this from Viber:
'Once you and your friends install Viber, you can use it to talk and message as much as you want. Talk, message, and talk and message some more and it's all free*!
* When you use Viber on a 3G network you might incur operator data charges or internet access fees.'


And also roaming charges?

Viber basically just uses up your normal data allowance.

Yes, but what does that mean!?

Basically Voice Over IP, another Skype

What does that mean? (I don't know much about Skype, never used it). Sorry, I just don't know anything technical about mobiles...

Basically, I just want to know that if me and my contact both use Viber, will it be free, no additional/hidden costs? As we both have unlimited internet.

As you say you don't know much about phones, do you definitely have Unlimited 3G internet, or is it a plan that says Unlimited but that's actually limited to a certain amount?

Wi-fi will be fine (unless your home broadband is on a limited package and you use this a lot as well as your regular use).

Basically, if there's a maximum MB or GB usage amount on your 3G or your home broadband (wi-fi) then you'll need to keep an eye on how much data the app is using.

Viber will use your phone's internet to make the call, this will not incur any charges regardless of whether the call is international or local. As long as you are sure you have truly unlimited data then you will be fine. If your phone data plan has a cap always keep an eye on how much you have left. Same with WiFi, make sure your WiFi is unlimited usage a month. The only time you would be charged would be if you went over your data allowance and that would be by your network operator.

Unlimited = No charges for using Viber / Skype etc
Capped GB = Stay within limit & there will be non charges, exceed limit you will be charged.