We are having some issues with UC520. Various IP SPA508g phones will not allow outside calls on PRI. The phones will run fine then all the sudden no go. You press 9 dial the number and you get dead air. If you reboot the phone that seems to fix the problem for a short while. Then we got issues the VM pilot DN3099 same deal some phones go through to VM some do not.
I am getting tired of rebooting phones.