InPhonic today is partnering with its biggest resale competitor Amazon.com, announcing today that it will take over the wireless service storefront of the country’s largest e-tailer.

InPhonic is the leading reseller of wireless service in the U.S. through sites it runs like Wirefly as well as white label portals it runs for carriers and third-party retailers. Amazon’s online sales might has always made it an formidable number 2 competitor, hampered only by the fact it can’t provision and activate phones through its web portal, said David Steinberg, CEO of InPhonic.

“They don’t activate phones, but now that they’ve decided to do it, they’ve turned to us,” Steinberg said. “For us this is a seismic shift in our business.”

Amazon has an estimated 50 million customers and one of the strongest web brands in the world. In addition to Amazon, InPhonic is working with several other online retailers including Overstock.com. Steinberg, however, doesn’t view that as a competitive problem. In fact, he said, InPhonic’s whole business model is based on pitting competitors against one another, allowing customers to comparison shop between carriers.