What actually happened is that AT&T and Verizon were penalized for mishandling customer location data by the FCC. They paid their fines, but attempted to contest them because they were levied by an administrative action, without a jury trial (which they claim would violate the Seventh Amendment), drawing an analogy to the case SEC v. Jarkesy, in which the Supreme Court ruled that the SEC could not impose civil penalties without a jury trial.
However, the Court ruled in this case that, since the law in question allowed the companies to appeal their fines to a jury trial, that the penalties are constitutional. This is unlike SEC v. Jarkesy, where the SEC civil fines in question had no provision for appeal to a trial by jury.
Furthermore, the Court clarified that the companies have the option to settle their obligations by either paying the fine, or by not paying the fine and appealing. The companies had claimed that the text of the law required them to pay the fine before their appeal, but the Court disagreed.