> We have determined that Twilio Inc. (Twilio) is apparently originating illegal robocall traffic on behalf of one or more of its clients. As explained further below, this letter provides notice of important legal obligations and steps Twilio must take to address this apparently illegal traffic. Twilio should investigate the identified traffic and take the steps described below, including blocking the traffic if necessary, and take steps to prevent Twilio’s network from continuing to be a source of apparently illegal robocalls. Failure to comply with the steps outlined in this letter may result in downstream voice service providers blocking all of Twilio’s traffic, permanently.

Seems like quite a reasonable request. Put in an effort. Outline what those processes are and stay on top of them.