If you try calling someone and they D/C during the dialtone, the phone keeps calling them and the dialtone plays after you hang up. Also this:
[ERROR] gamemodes/ocrp2/gamemode/client/vgui/phone.lua:564: Tried to use a NULL entity!
1. Nick - [C]:-1
2. DoClick - gamemodes/ocrp2/gamemode/client/vgui/phone.lua:564
3. unknown - lua/vgui/dlabel.lua:206