Got a call tonight at about 8:20pm. Answered because I have friends in Maryland. "Air duct cleaning" call. I told them my number was on the Do Not Call list and hung up.
I started getting calls from this number with Caller-ID of "Oxon Hill MD" on 1/14. Since then it's called on 1/21, 1/23, 1/25, 1/26, and 1/27.
I think something happened a couple of week ago because the frequency of garbage calls to my landline has greatly increased and I'm starting to get calls on my mobile now as well (4 yesterday alone). I now ignore or reject all calls from numbers I don't recognize on the assumption that any real caller will leave a message. Scammers never do.