Inbound calls from Asterisk and Test around midnight
 

The last couple of weeks I receive calls, mostly late at night (CET), from "Asterisk" and "Test".
The last one I got an hour ago. When I once again checked the sip info page of my PAP2T, the last caller was Asterisk.
I did answer the phone, knowing I would only listen to dead air. So, dead air it was.
Not that I have a choice; not answering the phone means simply it just goes on ringing.
The pattern is always the same, at least the last three nights: the phone rings until I pick up, I end the "call", then the phone starts ringing again, I pick up and end the call again. After that it's over until the next night.

I know at least of two other Voxalot users, experiencing the same strange calls.
Anyone else with the same experience?

Or does anyone have an idea of where the calls come from, what or "who" initiates the calls?

I would appreciate some help, please.

Thanks,
Zoe