AT&T announced that it will be phasing out its 2G network by 2017.
The mobile carrier said that the move is to make room for 3G and 4G technology on its limited airwaves.
The Dallas-based company said that these customers will be forced to upgrade over the next few years, reported PC Magazine.
More from GlobalPost: Old problems plague New India
"As the wireless industry continues to mature, we believe that future wireless growth will increasingly depend on our ability to offer innovative services and devices and a wireless network that has sufficient spectrum and capacity to support these innovations and make them available to more subscribers," said AT&T in a statement.
"While we are continuing to invest significant capital in expanding our network capacity, our capacity constraints could affect the quality of existing voice and data services and our ability to launch new, advanced wireless broadband services, unless we are able to obtain more spectrum."
Currently about one third of customers use 4G phones.
In other news, AT&T recently acquired carrier NextWave, a small company that has two bands of spectrum.
Forbes wrote the deal was mainly to prepare for an upcoming spectrum crunch that carriers will soon face.