If you are getting truly unsolicited calls or messages you can email Twilio and ask them to check it out. However, having worked there and looking up numbers I was getting contacted by, I never had a positive match in Twilio's inventory.
I understand these calls could be coming from anywhere, and Twilio isn't the only game in town. Since I am familiar with Twilio, and I know how easy it would be to put up a robo caller, I can't help but suspect. Its what I would use to do it. A self-service search tool would be neat, or maybe a tool to see if any Twilio services have called your number recently. Despite the annoying calls, I don't want to bother Twilio staff with inquiries.