Unions representing about 40,000 employees of Verizon Communications Inc. said they will go on strike on Wednesday if a new contract isn’t reached, escalating a dispute over the company’s shrinking legacy business.

The employees, who work mostly on the company’s landline phone and Internet operations along the East Coast, have been working without a contract since August.

The workers are represented by the Communications Workers of America and the International Brotherhood of Electrical Workers. In 2011, a strike lasted two weeks before a new contract was reached.

The unions say they are trying to improve pension benefits and prevent Verizon from outsourcing jobs to contractors. The company, which has about 178,000 total employees, is looking to reduce retirement benefits and health-care costs.

“We’ve worked hard in negotiations to find common ground, but working people at Verizon and across the country have had enough of the corporate greed that is destroying our families and our economy,” said CWA union official Dennis Trainor.