In the two weeks since Elon Musk tried to reassure advertisers that Twitter wouldn’t turn into a “free-for-all hellscape” under his ownership, a number of those advertisers do not appear to be taking him at his word. Pfizer (PFE) General Motors (GM) and United Airlines (UAL) are just a few of the brands that have said they were pausing their ad spending on the social-media platform following Musk’s $44 billion acquisition. Major ad agencies are recommending that their clients hit the brakes as well.