Here are the facts:
Atomic Wallet was created in 2017/2018 by Konstantin Gladych—the former CEO and co-founder of Changelly.
ChangeNOW and Changelly serve as swap partners within Atomic Wallet. The swap feature is powered by these two services; in other words, when you exchange a coin in Atomic, it actually sends a request to ChangeNOW to execute the trade.
In short:
Atomic = a wallet (created by Konstantin)
Changelly / ChangeNOW = exchanges used by Atomic to facilitate swaps