Federal regulators say Verizon Wireless has agreed to pay a fine of $25 million and at least $52.8 million in refunds to customers who inadvertently racked up data charges on their phones over the last three years.

The Federal Communications Commission says the fine is the largest in its history.

To forestall action by the FCC, Verizon Wireless said earlier this month that it would issue refunds, mostly of $2 to $6, to about 15 million subscribers.

The FCC started asking Verizon Wireless last year about $1.99-a-megabyte data access fees that appeared on the bills of customers who didn’t have data plans but who accidentally initiated data or Web access by pressing a button on their phones.