USA based AT&T has announced that it expects to close its GSM networks by 2017 at the latest.

In a filing with the SEC, the company said that at the end of June 2012, just 12 percent of their postpaid customers were using 2G handsets. The company didn't break down the figures for its prepay customers, although its prepay base is only around 11% of its total customer base anyway.

AT&T says that it is facing significant spectrum and capacity constraints on its wireless network in certain markets. They also expect such constraints to increase and expand to additional markets in the coming years. As such, they plan to move forward redeploying radio spectrum currently used for basic 2G services to support its 3G and LTE networks.

Throughout this multi-year upgrade process, the company said that it will work proactively with customers to manage the process of moving to 3G and 4G devices, which will help minimize customer churn.

They do not expect this transition to have a material impact on operating results, but will continue to evaluate the financial impact of transitioning customers from 2G devices to 3G or 4G devices.