Thanks For your reply
the problem is iam already connected and i have no problem connecting to sip account but although it is connected when i try to make a sip call it always says (unauthorized call)
i think maybe there is an option blocking the sip from working!
i don't really know about the (unauthorized call) problem and it seems that no one faced it before i guess because i also searched on google and nothing came :s
what should i do?