Galante received a voice mail message from a company representative that he posted on his blog.
The message said, "If you sent any further e-mails to Randall Stephenson, a cease-and-desist letter may be sent to you."
The exchange brought a quick deluge of comments on Galante's Twitter page.
And it brought a reply from AT&T's public relations people.
"We apologized to our customer," the statement said. "We worked with him to address his questions and concerns. This is not the way we want to treat customers. From Facebook to significant customer service channels, AT&T strives to provide our customers with easy ways to have their questions addressed."
Southern Methodist University Cox School of Business expert Mike Davis said the exchange would have been a minor issue a few years ago. But information moves much faster these days on social networks such as Twitter and Facebook, partly through AT&T’s own technology.
"If AT&T was just sort of this monolithic monopoly like in the old days, they could tell somebody like this to go away," he said. "AT&T is in a competitive business right now, and they know it, and that's why they so much regret their mistake and they're so anxious to make things right."