A customer networks and his Virtual PBX!

A customers network and his Virtual PBX!
Most the time we get new customers they configure their PBXs and we do not here from them again! Other times tickets go back and forth for days. We get the occasional ticket from existing client here and there but mostly new clients put in the most tickets.
Recently we got a new client, we installed the server with Trixbox upgraded it and handed the Virtual PBX off to the customer. They were having all kinds of problems and did not understand why. So we installed Elastix. At first they said they were having no issues and it was working. We resolved the ticket. Later on that day they were getting disconnected from the PBX phones would go offline and then come back online. We troubleshot the Virtual PBX from our end and did not see any connectivity issues, hardware issues, or software problems beyond configuration. The customer was getting very frustrated stating that it worked at their office fine etc. Then she had us install PBXinaFlash. Everything was working great for about six hours and BAM there was another ticket! We again asked a hundred questions and got very little answers. Finally the customer told us every time we reinstalled she had rebooted his router. She rebooted it again and the phones came back online. Keep in mind every time we did traceroutes to his network and his provider everything looked great from his Virtual PBX. His phone would connect then just show offline. She ended up buying a new router that was VOIP compatible. We could not ever get her to do a ping or traceroute to her virtual server. We left PBXinaFlash on the server as by default it installed fail2ban and iptables. She needs security I do not think she knows how to ssh into her virtual server but she can use the web interface webmin, freepbx etc!