This is bizarre. After you pointed out my error, I went to Wikipedia to verify before saying anything more. I was wrong originally; you, me, and your link all know it. But Wikipedia says it was AT&T that first carried the iPhone [0]. I assume it's because AT&T bought Cingular, but it feels off not noting that it was branded under Cingular instead of the separate (at the time) AT&T.
It's an eerie feeling finding errors or omissions in what is commonly used as an irrefutable source of truth in the modern world. I appreciate the correction though!