the unit supports voip sure. sprint has voip services (as does ATT verizon i believe), but it uses different equipment. what you have is JUST for cellular. you are not paying for voip service. they probably had you go to a voip site because its in their notes to do so.
we can go round and round the berry bush
, however if you are satisfied with your system then great. I simply dont want you to have mis-information about what the unit is and does.
i dont pay anything at all for the unit. its zero. im not sure what number you are paying for, but the number assigned to the unit is not a number you can call to the unit.