Decades ago, (I think it was MCI rather than Sprint) had a solution to eliminate the cost of long distance through the "phone company". They came into your office and inserted a box between your phone and the wires going to the phone company. The box was smart and if you dialed a long distance number (more than 7 digits), it dialed a special number instead. When that number answered, the box dumped your dialed digits to the machine that answered and your call was completed using their equipment rather than the phone companys equipment. They charged less for their call than the phone company.
The Obi110 is similar to that device. If you do not connect it to a wired phone provider, the calls are routed through the internet using a provider of your choice. If you do have a wired provider (or other service that looks like a wired provider) you can insert an Obi110 between your phone and that provider. By configuring the Obi, you tell it which calls to route through which provider.