Very occasionally, you may experience calls on your VoIP phone that look as though you have called yourself from an extension you don't recognise. Sometimes these calls can present like an ordinary call as well, but you can't see them in your dashboard.
These are known as Ghost Calls & are unfortunately a well known problem in VoIP; they're very similar to autodiallers on a regular analogue line. They have nothing to do with your provider or your equipment, they're just extremely annoying when they become regular!!
Ghost Calls don't pose any significant risk to your phones or network so long as you make sure you keep your firmware updated & you can also update your sip port to make it harder for the Ghost Calls to get through. Most sip ports are set to 5060 by default so by changing this port to another e.g 6085, means the Ghost Calls won't be able to get through so regularly.
On Grandstream phones you are able to eliminate ghost calls entirely by changing a setting on the phone to disable IP to IP calls.
Under the account settings go to -> SIP Settings -> Security Settings. Then enable the options “Accept Incoming SIP from Proxy Only"
If you'd like any help with changing any of these settings, please do get in touch!