Here is my scenario to set up the 3cx phone system. But I got some problem in the setup. I have no problem in main office, I can dial to 3CX ext and dial to analog PBX from the ip phone. The gateway I use is Grandstream GXW4104 in the main office. So here is the problem. 1. In the branch, I use oivatech (i forget the type, but its old one), the registration status is success to connect 3cx, but when I try to dial from ip phone to analog pbx, I just hear the voicemail box sound. When I dial 200 from analog phone, nothing happen. I wonder what is wrong because the setting in 3cx is same with the main office. Is the oivatech not support 3cx? 2. Can I use the scenario above? So, when I dial 200 from the main branch and enter 9108, I can connect to the branch Analog phone. I try in the main office, dial 200 and then enter 8108 (108 is one of the ext in main office) but I just got the message that the number i dial (8108) is unregistered. Any additional setting for this scenario?