I have an ATA spa 1001 system connected to my modem/router, and I am currently connected with slingshot's VOIP. All my ports which use VOIP is open. My outgoing calls are alright, but whenever someone calls me, its either going to my answering machine (I dont get any rings or calls from anyone in auckland) or I dont hear them (the line is blank) but they can hear me properly. My line is an 09 digital naked dsl but im in napier! Slingshot said that theres no need to change it. Is there a setting in my spa1001 that I am missing which causes the callers voice to not come up?