hello!
i ve just downloaded zoiper, and i m trying to make a test to see if it works...
but when i try to make a call it says that the number isn't available (and i know it is)
thank you for your help :)
Zoiper is just a soft phone, in order to place calls you need to register with a VOIP provider.
See this list for an (incomplete) choice of providers:
http://www.zoiper.com/en/voip-softphone/download/zoiper3/providers