The idea of using a VoIP provider would be to _avoid_ using one's phone, e.g. to get better rates... And the reply-to number, it's unfortunately not the way tel

The idea of using a VoIP provider would be to _avoid_ using one's phone, e.g. to get better rates... And the reply-to number, it's unfortunately not the way telcos work... and changing all the infrastructure for this would be very very expensive.