@shin
linphone is very buggy. There are other SIP phones that might be more reliable. Check to see if the ports I mentioned are all open http://www.canyouseeme.org

Umm I'm gonna be away for awhile but the first thing I recommend is to clear all the settings in linphone and then re-enter the info. Make sure the ports are working. Does it say when you call via 1000@sipgate.com "account setup...goodbye"? There is also a test phone link in the sipgate.com settings. If this doesn't work and I'll have to check through the my instructions when I get back, I'll go ahead and and do the activation for you if you'd like. After activation you can use Gizmo or whatever.