Does the FCC have the authority to do that or are they beholden to Congress as is so often the case?
Part of the conservative push to deregulate is to argue that government agencies are incompetent but the reality is that they've constructed a system where these agencies literally lack the agency to do anything more than write a nasty letter.
This is only valid if it’s a US company and many of these are originating outside of the US. Many shady companies outside of the us simply ignore the fines.
Except, when it comes to prosecuting people they usually make a deal where they pay a $50k fee or whatever, or they just don't have jurisdiction over the spammers and they'd rather sanction Russia than sanction India or other countries that are originating a lot of the SMS and robocall spam.
https://www.fcc.gov/spoofing