Mystic — Bank of America has announced that it will be closing both of its Mystic branches, located at 54 W. Main St. and 31 Williams Ave., on May 15.

The West Main Street location is a financial center in the stately, circa-1930 building next to Mystic Pizza, while Bank of America describes the tiny Williams Avenue location across from Sea Swirl as an "autobank," spokesperson Tara Burke said.

The ATM at the autobank, which Bank of America leases from Shoreline Branches LLC, will remain open. Bank of America owns the West Main Street financial center, and Burke said the building will go up for sale.

Financial center and autobank customers received letters early last week informing them of the respective closures.

"We have banking associates ready to help you at other locations, and thousands of ATMs, some right in your area," the letter stated, pointing to Bank of America branches at 738 Long Hill Road in Groton and 9 Franklin St. in Westerly.

The Groton and Westerly branches are respectively about 5 and 11 miles away from the Mystic financial center.

Burke said the decision to close the Mystic branches came because customers' banking habits have changed over the years.

"We saw more and more customers utilizing these online and mobile channels to do their everyday banking," she explained. "You can make payment to your credit cards on it, you can transfer money."

Bank of America has 24 million active mobile banking customers, she said.

Leaving the autobank on Friday, Frank Heibler commented that he was upset to hear of the closure, considering he lives nearby and had been banking at that location for 20 years.

Not wanting to drive farther, Heibler said he is closing his account and switching to Chelsea Groton.

In December, Bank of America sent notices to clients informing them that the 68 Boston Post Road branch in Waterford would be closing on March 27. At that time, Burke also cited increased mobile banking as a reason for the closure.