I am looking at a VOIP app for my Samsung Galaxy S3.

I am a bit confused. I have looked at the apps and you still need to sign up with a provider, is there aa provider with an app?

Also on the provider website there is a list of call charges, I thought that you simply used a wifi internet connection to make free calls?

What am I missing?

Any help much appreciated.

VOIP is simply a transport mechanism for the call as opposed to the old copper comms.

You still have to pay for that mechanism, be that for details to login to an internet PBX or using Skype for a more peer to peer system.

Try Viber. Provided you and the person being called have a good internet connection it works well. We use it a lot in our company.