I have a situation where there is a remote site VPN set up with a Sonic Wall TZ180. The main site has a Sonic Wall NSA3500. This was set up by the customers IT dept. We deployed 7-9608 phones. The phones are registered with the IPO. We have intermittent issues where there is no dial tone. Then you press call app B and get dial tone. Or no dial tone at all. And while this is going on inbound calls will be routed to voicemail. We can reboot the phones and be ok for a while. Any suggestions would be appreciated.