AT&T had said on July 7 it was working with network equipment maker Alcatel Lucent SA to fix the glitch, which it said affected less than 2 percent of its mobile user base.
The No. 2 U.S. mobile operator said on Monday it had begun rolling out an Alcatel-Lucent software patch that would restore uplink speeds for its high-speed data services that depend on so-called HSUPA technology.
This patch will be deployed on a phased basis over the next two to three weeks, AT&T spokesman Mark Siegel said.
AT&T, the exclusive U.S. provider for iPhone, said the iPhone 4, the latest Apple device, was the only smartphone that runs on its HSUPA network.
AT&T shares were up 2 percent, or 51 cents, at $26.05 in early afternoon trading on New York Stock Exchange. Apple shares were down 94 cents, or 0.35 percent, at $259 on Nasdaq.
(Reporting by Sinead Carew; editing by Andre Grenon)