In 1879 , this company joined with the New England Telephone Company to form the National Bell Telephone Company . In 1880 , they formed the American Bell Telephone Company , and in 1885 , American Telephone and Telegraph Company ( AT&T ) , still a large company today . The establishment of the International Bell Telephone Company in Brussels , Belgium in 1880 , as well as a series of agreements in other countries eventually consolidated a global telephone operation .