AT&T customers in Portland, Ore. discovered their cell phone bills increased this summer because the wireless company decided to pass along the costs of Portland’s Clean Energy Tax to its customers. Except AT&T is exempt from paying the tax, but wants customers to pay to recoup costs the phone company is not paying.

Portland’s Revenue Bureau told Willamette Week it classifies cell phone providers as utilities, and they are exempt from the tax.

Scott Karter, a manager in the Revenue Bureau, said it was up to AT&T to decide if it will refund customers for the charges it has collected since August.

“The code does not specifically address amounts that might be over-collected from customers,” Karter said.

AT&T had no comment.