Had 7 calls from this number. I route 'em to SPAM in my google voice account. Obviously an automated system otherwise a "human" would realise that there's never going to be an answer!

Keeps calling me collect asking me to accept the charges!

Nuisance calls. Dead air when answered.

Calling back, indicates is an automated promotion system from Comcast.

I've gotten 3 calls from that number, they don't leave messages and nobody talks when the call is answered.