I just posted about Twilio and their vague AUP yesterday: https://news.ycombinator.com/item?id=36603591
There are a host of reasons why your account can be suspended or terminated, all at the judgement of Twilio as to whether you actually violated something or not, and there doesn't seem to be any recourse.
Personally, I've dropped interest in Twilio for a project I'm working on and will be going forward with Telnyx.