Here is what I heard from VOIPO Support. The explanation was good enough for me and I haven't seen the issue since then.




>
> I understand, it's possible that certain types of calls, usually from
> telemarketers or similar agencies, use an intermediary service to route
> these calls. This sometimes can involve two separate numbers to route the
> call to the destination number; the source number and the forwarding
> service's number used. When this type of call hits our call details system,
> it can register the call unusually and display how the call is perceived in
> Call History. Although this is not a common occurrence, it has been known
> to take place on occasion.
>
> As we investigate deeper, we can see in the SIP logs that the call was
> purposely made to your VOIPo number and reaches your location. Usually if
> it's an instance where someone else is attempting to utilize your service,
> we can see that information in our call traces.
>
> Do let us know if there are any further concerns we can address for you.
>
> Kind regards
>