For three months, he made his $410 loan payments without a hitch. But in early May, Wells Fargo sent both borrowers a letter saying it had not received the necessary documentation showing that the car was insured. A second notice saying the same thing followed a month later.

When the first notice came in, Mr. Dunlap was recovering from a stroke, he said. Still, he began calling Wells Fargo to tell them he already had insurance. He was unsuccessful, he said, because he’d be kept on hold for long periods and often got disconnected.

Ms. Temple of Wells Fargo said: “We recognize there were a number of customers who experienced difficulty verifying with Wells Fargo and our vendor if they had insurance and we are sorry that Mr. Dunlap experienced this challenge.”

On July 1, Mr. Dunlap’s loan statement showed, Wells Fargo charged $1,079 for insurance on the car — the first time such a charge had appeared. The insurance, a year’s premium, took effect in March when he bought the car.

Mr. Dunlap said he didn’t know about the charge and records show he made his regular loan payment in July. But because he owed the additional $1,079 for insurance, he fell behind. Late fees began accruing, and his problems on the loan were reported to credit bureaus.

He made more calls to Wells Fargo. “I’d talk to one person in one state, another person in another state; I’d send them papers,” he said. “There were so many different people involved, the information doesn’t get to the right sources.”

Some Wells Fargo letters came from Phoenix, Ariz., while others were postmarked Irvine, Calif., and Irving, Tex.