I've received lots of calls from the +1 (978) 505-xxxx saying Concord, MA. (Also +1 (978) 233-xxxx from "Hamilton, MA"). I believe most if not all the 505 numbers were assigned as mobile numbers, probably Verizon. The 233's are probably the same.  They keep changing the last 4 digits, maybe hoping you'll run out of blocking number capacity? I think I answered once or twice and got either a "health alert" system pitch for elders or a "lower your electric rate" pitch, or just silence.