Unifi VOIP terminates at the BTU on VLAN400. It won't affect any VOIP devices you have running over the Internet. The router provided by TM is not even aware of the VOIP VLAN nor does it handle any SIP communication from TM's VOIP service. The only thing that would screw up your VOIP/SIP client would be the SIP ALG on the DIR-615 (I'm not sure if they have it working properly).