To get them to stop calling set up your fax machine to call them 24-7. they will never call again because there line will be busy for ever with fax calls.
I believe this number belongs to a market research company doing surveys for Comcast and others. If you return the call you are likely to get a voice mailbox that is usually not attended so always full.
Just got a call from this number. Said Providence, RI. Didn't answer but thought I'd wait for someone to leave a message, but it only rang three times and then they hung up. I DO have Comcast, so maybe it was them. If they left a message and said they were doing a Comcast survey, I might actually call them back. But if they're just going to hang up and use a number that you can't call back, I think that's SLEAZY.