Charles M. Skibo, the former president of US Sprint, was fired last week because he failed to correct computer problems that caused the company to lose $76 million in its second quarter when customers were incorrectly billed for long-distance calls, sources close to the company said yesterday.

At a press conference to celebrate the first anniversary of US Sprint, which was created when GTE Corp. rolled its money-losing Sprint into a joint venture with United Telecommunications, the company's new president, Robert H. Snedaker Jr., said the task was to clean up operations to keep customers satisfied. Between 20 percent and 30 percent of US Sprint's five million customers are businesses, which generate most of the industry's profits.

"It hurts your reputation to a degree" to have billing problems, Snedaker said yesterday. "I think he {Skibo} had the marketing capability, but we ran into backroom problems because of growth. Billing was the main problem."

Snedaker said the problems grew out of trying to merge duplicate billing systems while the company's customer base grew rapidly. He said he had not had time to identify specific billing problems.

"Skibo was a marketer. They needed some operations strength," said one executive of US Sprint, the third-largest long-distance company. He said the company found that strength in Snedaker, the former vice chairman and chief operating officer of US Telecom.

Sources close to the company said US Sprint recently sent out 13,000 bills to customers who had already settled their accounts. Ed Carter, senior vice president of sales and marketing at US Sprint, said other problems have included underbilling and delayed billing.

"If you make telephone calls in August, September, October, and don't get a bill until June of next year ... all of a sudden your budget goes out of whack," he said. "All of a sudden they {customers} say, 'We're not going to pay.' "

Asked if some customers had dropped US Sprint, Snedaker said some were "frustrated."

Skibo, who held jobs at US Telecom and MCI Communications Corp. before joining US Sprint and who is known as a savvy marketer, could not be reached for comment yesterday. A statement from GTE last week said he "resigned to pursue other business interests."

At the time, GTE also announced a $350 million pretax charge in the second quarter that will be split evenly between the partners to reflect both uncollectibles and a write-down of the old long-distance network Sprint built. Sprint has transferred more than two-thirds of its customers to a 23,000-mile-long fiber optic network that uses glass strands to transmit information using bursts of light. More than 90 percent of Sprint's customers will have been transferred by the end of the year.

Howard Anderson, president of the Yankee Group consulting firm, said billing problems were a fact of life for almost every long-distance company except American Telephone & Telegraph Co. Skibo had been at MCI when the same problems were being worked out, Anderson said.

"He had solved their computer billing problems and database problems, but this may be trickier than it looks," said Anderson. The companies might have done better hiring outside consultants to solve the problem, but they have been "capital starved," he said.

Anderson said the parents that have invested billions of dollars in US Sprint could "downsize" the operation if it doesn't turn a profit soon. "They are both afraid this is Vietnam, like a quagmire... . They are losing their patience."

William T. Esprey, president of United Telecommunications, would not say when US Sprint might turn a profit. "We said we would lose significant money in the first half {of the year} and show significant improvement in the second half," said Esprey.