Its not “guilt by association”; Twilio has, under the relevant laws, a positive obligation to prevent illegal use of its platform on pain of disconnection.

Note that this isn't a "we didn't know about this" and is part of the "this is what you sign up for when you're a telephone service provider."

47 CFR § 64.1200 - Delivery restrictions. - https://www.law.cornell.edu/cfr/text/47/64.1200

> (4) A provider may block voice calls or cease to accept traffic from an originating or intermediate provider without liability under the Communications Act or the Commission's rules where the originating or intermediate provider, when notified by the Commission, fails to effectively mitigate illegal traffic within 48 hours or fails to implement effective measures to prevent new and renewing customers from using its network to originate illegal calls. Prior to initiating blocking, the provider shall provide the Commission with notice and a brief summary of the basis for its determination that the originating or intermediate provider meets one or more of these two conditions for blocking.

There are some other fun things in section (n) about the requirements for a voice provider.

> (n) A voice service provider must:

> (2) Take steps to effectively mitigate illegal traffic when it receives actual written notice of such traffic from the Commission through its Enforcement Bureau. In providing notice, the Enforcement Bureau shall identify with as much particularity as possible the suspected traffic; provide the basis for the Enforcement Bureau's reasonable belief that the identified traffic is unlawful; cite the statutory or regulatory provisions the suspected traffic appears to violate; and direct the voice service provider receiving the notice that it must comply with this section. Each notified provider must promptly investigate the identified traffic. Each notified provider must then promptly report the results of its investigation to the Enforcement Bureau, including any steps the provider has taken to effectively mitigate the identified traffic or an explanation as to why the provider has reasonably concluded that the identified calls were not illegal and what steps it took to reach that conclusion. ...

> (3) Take affirmative, effective measures to prevent new and renewing customers from using its network to originate illegal calls, including knowing its customers and exercising due diligence in ensuring that its services are not used to originate illegal traffic.

The second Twilio press release (Twilio Achieves Full Compliance with STIR/SHAKEN Protocols to Combat Illegal Robocalls) is dated July 22, 2021.

The FCC complaint has calls dated July and August of 2022.