The examples that follow are a snapshot of the work I've done in my current job of leading the user experience, graphic design, and front-end development of the site for U.S. Cellular, a $4B cellular service company with roughly 5 million customers. The overall architecture was built in mid-2010, prior to wide-spread industry use of HTML5/CSS3 and Responsive Design. Please note that the state/content of the pages on the live site will change over time from what you'll see below.
The most challenging aspect of managing the e-commerce experience for a wireless company is enabling shopping for non-traditional e-commerce products. Consider the complexity that goes into selecting all of the aspects of a multi-line wireless account. In a retail setting, a salesperson can walk customers through the vast array of choices. On-line, despite robust support tools and chat, all of that complexity has to be abstracted as much as possible to encourage customers to convert on their own.