The Chesapeake and Potomac Telephone Co. of Virginia filed a request for a reduced rate increase yesterday, dropping its revenue requirements by $39.4 million from the $133.5 million request for which it had filed in August.

Telephone company officials said that divestiture of some of its telephone sales and leasing business, improvements in the stock market and reduced borrowing costs led to the lowered rate request.

The company's initial request would have increased Virginia rates across the board by about 19.2 percent and produced a return on equity of between 18 and 19 percent. The lower request will add about 11.22 percent across the board to customer bills and is intended to produce a return on equity between 16 1/2 and 17 percent.

A residential customer with the flat rate would pay approximately $14 a month compared with the $12.75 rate now in effect. A business customer's bill will increase by 11 percent from $16.85, according to C&P.

The divestiture is a result of a 1980 decision that required C&P and other companies to set up a separate subsidiary for handling equipment. American Bell will be the deregulated, separate subsidiary that sells equipment. Because of that, some staff and assets will be transferred from C&P to American Bell.

C&P took similar action in Maryland last month.