said by fiberguy:
And, data.. there is still an issue of ROAMING at large here.. and that's never going to change for a long time.. networks don't have "nationwide coverage" of their own.. they have sharing agreements.. that makes up the illusion of a "nationwide network".. still, they're buying and trading time from one network to another.. unless and until they have true nationwide coverage, which would honestly be a complete waste of money, you're going to run into snags from time to time.
The problem with ROAMING is that you can get charged for it even when it has no cost to either your home or the remote network. As you note the actual cost is usually covered by the peering agreements (or equivalent). The only actual cost is when customers of CellCo 1 do more data roaming on CellCo 2's network than CellCo 2's users do on CellCo 1's network. Otherwise the amounts balance and it is as if all the usage was by the users of the connected-to's network.