It added it would be encouraging current distribution employees to make the 90-mile (145km) move with the company, but would proactively help those that could not to find other employment.
The telecom giant said about 12% of its contract wireless customers, or roughly 8.4 million people, were using 2G handsets at the end of June, but it will work "proactively" in coming years to move them to more advanced devices.