Pennsylvania Attorney General Dave Sunday announced Wednesday the next phase of a national crackdown on illegal robocalls is underway, this time targeting four major voice providers accused of allowing unlawful calls to reach consumers.

The effort, part of the bipartisan Anti-Robocall Multistate Litigation Task Force, directs Inteliquent, Bandwidth, Lumen and Peerless to strengthen protections across their networks. Sunday said the companies must do more to block scams that can expose Pennsylvanians’ personal and financial information.

In August, the task force issued warnings to 37 smaller providers.

Since then, 13 companies have been removed from the Federal Communications Commission’s Robocall Mitigation Database, 19 no longer show up in traceback investigations and at least four have cut ties with high-risk customers linked to illegal call traffic.