NEW YORK (Reuters) - Cingular Wireless, a venture of AT&T Inc. and BellSouth Corp., said on Monday it would start charging customers with older phones an extra $4.99 monthly fee as early as September unless they upgrade their phones as it moves toward using a single network technology. The biggest U.S. wireless service, said the fee would apply to about 4.7 million subscribers, or about 8 percent, of its 57.3 million customer base unless these users upgrade their phones. It is part of Cingular's plan to phase out phones based on older TDMA and analog technology, the technical standard for...