Nimbuzz!

Nimbuzz is a social communication tool where you can have conversations in real time with friends and other users from anywhere in the world. Use Nimbuzz's simple interface to contact friends from different social networks (as long as they've already downloaded the PC, Android, or iOS version of the application).

In addition to friends, you'll have access to chat rooms with users you can talk to even if they aren't on your contacts list. This application also lets you create group chats with specific friends, and sync up with Facebook chat and each contact's status so you know who's online.

You can also make phone calls after verifying your phone number. The calls are free and the signal strength will depend on your data plan, as these are VoIP conversations similar to Viber, Skype, and Line.