Apple’s Official iPhone 3G Unlock

Traditionally, toll charges (a surcharge) can be assessed to the calling party in the U.S. based mostly on area code (a.k.a. the NPA, the first three digits of the phone number), which designates a geographic region of the country. Thus, the caller knows how much toll he/she will be charged based on the phone number. I live in Maine, which is in the northeastern part of the U.S., with a 207 area code. If I call a number with a 310 area code (mobile, landline, it doesn't matter), I know that's in Los Angeles, and I can expect to be assessed toll charges based on the fact that it is so far away.

Let's say I'm a mobile subscriber living in Maine, thus my mobile number will start with Maine's area code (207). Let's say my mom, who also lives in Maine, gives me a call. I happen to be roaming in Los Angeles.

When mom calls my mobile number, that call is routed to my home switch (a.k.a. the HLR). which then forwards the call using a technique called "call delivery," to a temporary number (called a TLDN) that was assigned to me by the visiting switch (the VLR), when I arrived in L.A. My home switch knows my temporary number because it was transmitted to it when I arrived in L.A., so it's no biggie for it to just forward the call.

Now - who should pay the toll on the "leg" of the call between Maine and L.A.? My mom didn't know I was in California, so is it fair to hit her with toll charges because she had no idea she was calling all the way across the country. Naturally, it makes more sense to hit the receiving end with the toll charges.

In addition to toll, we used to have a myriad of mobile network providers in the U.S., and they had varying roaming agreements which charged the home carrier different airtime rates based on the nature of the agreement between the carriers. Again, when I was in L.A., it probably cost my home carrier in Maine a lot more because the L.A. carrier would charge the Maine carrier an arm and a leg to host my call. Who is responsible for this increase in charges? There was no technical mechanism to pass it on to my mom, and it probably wouldn't be fair to sock her with it anyway, so it was charged to me, the recipient.

Now, with the advent of national plans with thousands of minutes, and with carriers consolidated down to a few national networks, and very low network costs, a lot of this doesn't make sense anymore. And some carriers (I saw that someone mentioned U.S. Cellular) are coming to their wits and abandoning this tradition. But getting huge, stodgy networks to change their ways and drop a cash cow for the hell of it when they have a virtual monopoly won't happen overnight.

TL;DR - it's a holdover from the early days when roaming cost more, and it wasn't fair to hit the calling party with surprise charges. It probably shouldn't be that way any more.