[gruez]

>you’d still likely get bombarded with robo calls to the MVNO number.

presumably all his calls are done through a VOIP app (he said astrix so probably SIP) and he can ignore all "normal" incoming calls, or is forwarded to his phone using a known number and he can ignore every number except that one.

[bronco21016]

In his setup, yes, this works as he does not have any phone number tied to the device. He’s using WiFi to connect to the PBX.

In the scenario where you use a cheap cell plan to have an always on data connection to the the PBX you will have to have some method of blocking all of the calls to the device number. I suppose you could have them all forward to the PBX and then your filtering could apply.