(CBS4) – Colorado’s attorney general is working with a group to put a stop to spam and “robocalls.” Last June, the FCC required all cellphone carriers to add what’s called identification authentication technology.

The goal was to prevent illegal robocalls, but so far it’s not been successful. In May, Americans got 4 billion robocalls.

Some experts say there needs to be more enforcement.

“The problem is the bad guys aren’t just sitting still. Instead of making up phone numbers, they’re getting real phone numbers. And now their real phone numbers are authenticated, they look like they’re good and they get through,” said Alex Quilici, CEO of YouMail. “You want enforcement to go not only after the bad guys, but some of the carriers that are supporting them.”

More than 50 attorneys are working together hoping to put pressure on the FCC to take action.