Wells Fargo says that it investigates all complaints of impropriety from its ethics hotline or other channels. But it added that until 2013, it handled each complaint about account fraud individually. It was not until three years ago that the company realized it had a broader problem, according to Mary Eshet, a Wells Fargo spokeswoman.

At that point, Wells Fargo began an internal investigation. By then, though, the issue had caught the attention of prosecutors and regulators. In May 2015, the Los Angeles city attorney filed a sweeping lawsuit against Wells Fargo over its creation of unauthorized accounts.

Last month, the bank settled that case and two related actions brought by federal regulators. Ms. Eshet cited the steps the company took in response to the scandal, including its move this month to drop the aggressive sales goals that employees said created pressure to act unethically.

“We have made fundamental changes to help ensure team members are not being pressured to sell products, customers are receiving the right solutions for their financial needs, our customer-focused culture is upheld at all times and that customer satisfaction is high,” Ms. Eshet said.

But former employees whose cases are detailed in lawsuits against the bank say that many of the managers at the branch level and above who heard their ethics complaints did nothing and are still there. Between 2011 and this year, Wells Fargo terminated the employment of 5,300 workers for creating as many as two million unauthorized bank and credit card accounts; around 10 percent of those worked at the branch manager level or above, according to the bank, but only one — an area president — had a high-level management role.

In 2009, Yesenia Guitron, a banker in the Northern California town of St. Helena, filed reports to her branch manager, to her branch manager’s boss and to Wells Fargo’s ethics hotline about a colleague who she said was opening and closing accounts without customer permission.

Those and other fraudulent acts continued despite her complaints, and were openly tolerated by the branch’s management, Ms. Guitron told Wells Fargo’s human resources department. In 2010, Ms. Guitron was called into her boss’s office and told she was being fired for insubordination.