AT&T Corp. agreed Tuesday to sell its customer services unit to Cincinnati Bell Inc. for $650 million in its latest effort to slim down and focus on its telecommunications business.

AT&T Solutions Customer Care has annual sales of about $400 million, handling customer inquiries for other companies and separate parts of AT&T. It has more than 9,000 full-time and temporary employees and nine facilities in the United States and Canada.

The sale is AT&T’s latest under new chairman and chief executive C. Michael Armstrong.

Last week, the long-distance phone giant announced it was selling its Universal Card unit to Citicorp for $3.5 billion.