Software Updates
Most handsets still need to be updated the old fashioned way - software has to be loaded onto the handset with special cables and equipment. For corporate and network security, manufacturers typically just sell this equipment to carriers or approved service centers, as well as maintaining it themselves.
Verizon, Sprint and Nextel all offer software updates for customers in their corporate stores. GSM operators typically leave updates up to the manufacturers. Nokia, Sony Ericsson Motorola and others will all update phones to the most recent available software at their service centers. While the carriers probably have a service center near you, manufacturers typically require that you send in your handset to their main service center for updates, often times with more than a week-long turn around.
To that end, independent service centers have popped up all over the US to update Nokia, Sony Ericsson or Motorola software. These agents have access to the same equipment and software versions as the manufacturers, and even if there's not one near you, they can usually turn your phone around quicker.