DO NOT sign up again, you will only leave yourself open for 31 days of calls from legally operating telemarketers along with the illegal ones and the outright scams. Registration is permanent until you change your number or request removal. They have always had "ways around that". Since it's inception anyone who dialed your number for any reason, legal or not, would get through to you. The DNC list and rules cannot prevent anyone from calling you much like a speed limit sign cannot prevent drivers from speeding. Callers have to chose to obey or not obey the laws telemarketers operate under and callers from outside US jurisdiction have little fear of being prosecuted for violating US laws.
I received a phone call and the caller hung up on me. The number they reached was my direct dial at work. I believe they were using an auto-dialer and dialing a sequence of numbers. When I called back the broadcast message said it was the "Auto Insurance Savings Center." The number broadcast the name: Novatel. I spoke to one of the customer service agents and he said that they do not call businesses.
Please be advised that these folks are selling auto-insurance in multiple states and it does not appear that they are abiding by any of the telemarketing laws. I was not provided the name of the company or the specific purpose of their call.
Even if you are interested in auto insurance, I would be careful about this outfit.