Verizon, can you hear me now? That’s the sound of angry mobile phone users who have prompted an investigation by the Federal Communications Commission into the company’s reported $50 million in “mystery fees” charged to cell phone owners.

The tab could go as high as $90 million in refunds to cell phone customers who were improperly charged for inadvertent Web access or data usage over the past several years. A defect in Verizon’s phone software caused customers to receive false charges of $2 to $6, which will be credited to customers’ bills in October and November. The refund is reported to be one of the largest in wireless network history.

In a statement on its website, Verizon Wireless said while most of the 15 million customers affected will receive credits of $2 to $6 on their October or November bills, some will receive larger amounts. Customers no longer with the New York-based carrier will get refund checks.

"Verizon Wireless values our customer relationships and we always want to do the right thing for our customers," said Mary Coyne, deputy general counsel for Verizon Wireless. "The majority of the data sessions involved minor data exchanges caused by software built into their phones; others involved accessing the Web, which should not have incurred charges. We have addressed these issues to avoid unintended data charges in the future."

Accusations of erroneous charges date back several years. In fact, the FCC began investigating the issue in January, according to a statement released Sunday by Michele Ellison, the FCC's enforcement bureau chief. At the time, the FCC asked Verizon Wireless about $1.99-a-megabyte data access fees that appeared on the bills of customer who didn’t have data plans but who inadvertently initiated data or Web access by pressing a button on their phones.

"We're gratified to see Verizon agree to finally repay its customers," FCC Enforcement Bureau Chief Michele Ellison said in a statement. "But questions remain as to why it took Verizon two years to reimburse its customers and why greater disclosure and other corrective actions did not come much, much sooner." The FCC will continue to look into those issues, including the possibility of additional penalties, Ellison said.