AT&T is still the “iPhone network,” according to numbers  from its quarterly earnings report. AT&T sold 5.5 million smartphones in the quarter, but 4.3 million of the smartphones activated were iPhones. That means the iPhone represented a whopping 78 percent of total smartphone sales (although some “iPhone activations” could have been hand me downs). Additionally, AT&T’s postpaid customers are almost 60 percent smartphone customers, which means AT&T’s iPhone customers represent a huge percentage of its base—nearly 5o percent and growing.

Verizon announced numbers last week including 3.2 million iPhones sold. While the iPhone is down significantly from the holiday quarter, it is up from 3.6 million activations in Q1 2011. Apple’s earnings will be reported at the end of the day today.