@matigo In the US, you're basically basically dealing with three networks now: Verizon, AT&T, and T-Mobile. There are also regional carriers in some areas, such as US Cellular out in this part of the world. Every other "carrier" (including the regionals for roaming out of area) buys airtime off one of these three. Dish (the satellite TV guys) is supposed to be building a fourth national network, but it remains to be seen if they can build anything that'd be considered functional or competitive to the other three.
In many respects, it's similar to the telecom situation in Canada, which is the only country that has worse competition (and pricing) than the US.