I do use VOIP.MS
Multiple sub-accounts and phone numbers, for two different families in different houses.
Panasonic cordless handsets throughout each house, connected to ObiHai Obi202 ATA boxes.

I have not noticed any unusual billings, charges or call records. I looked back several months.

I will say that actual home telephone service is becoming less compelling as time marches on. The number of people (and the frequency) which I communicate with using genuine telephone calls keeps diminishing.

FaceTime audio calling, or Skype or whatever app, seems to now be the norm for my outgoing ‘calls’. And for many of the people who call me.

For longer duration ‘app calls’ I sometimes use a headset with my iPad or iPhone.