Sprint has agreed to a $5.5 million settlement in a class action lawsuit over auto-dial calls placed in 2007 to its customers in Washington state, the law firm that led the case, Williamson & Williams, announced Monday.

The suit alleged that Sprint had violated the state’s Consumer Protection Act by sending auto-dialed prerecorded messages to its customers even after they asked to stop receiving the calls.

Sprint argued Washington’s state laws over the calls were preempted by federal regulations, but agreed to settle the suit in April without admitting its culpability.

“Sprint agreed to settle this case, determining this action would be in the best interest of our customers and our business,” a Sprint spokesman said in a statement yesterday. “In the settlement Sprint does not acknowledge liability nor admit any violations. Sprint places a high priority on respecting the wishes of our customers about how they prefer to be contacted.”

In addition to the financial settlement, Sprint also agreed to change a pre-recorded message provided to customers who called the operator in response to a promotional call.

Washington resident Sandra Palmer, a Sprint customer who received auto-dial calls for “several weeks” after asking the messages to stop, filed a class-action suit over the calls in 2009.

Customers covered by the suit are eligible to receive between $100 and $500 per call, up to $4,400.

The complaint encompasses Sprint customers between July 23, 2005, and June 13, 2011, in Washington state who received auto-dial solicitations less than one year after asking the operator to stop the calls, and Sprint customers in the United States who received solicitation calls more than 30 days after requesting a stop to the messages.

The settlement received preliminary approval from a district judge in Seattle last month.