I have a UCM6204 that has been in use for some time. We had 4 POTS lines and things worked with no issues but we were paying more in taxes than what the cost per line was costing us. Switched to a Sip line through the same phone company. have 4 channels via SIP. issue now is that if someone calls inbound, goes to someones extension who has an external number established in follow me, we cannot get the call to actually dial outbound. Calls in and out work just fine, its just when doing a transfer/follow me to an external number that originated off site.