I need help setting up a remote SIP extension on a 500v2. the phone connects perfectly when inside the office. when I leave the office I cannot get the phone to register. I have forwarded ports for rtp, 5060, 1718, 1719, and 1720. has anyone successfully gotten this to work? I am using a sonicwall tx205 as my router. I have tried two different apps, BRIA for android and 3CX for android with no success. any help would be greatly appreciated.