The thing with the "do not call" list is that while it might stop some telemarketers from calling, it just gives others more numbers to dial. A lot of places just don't care, they'll buy the list to get numbers to call. There's so many ways to circumvent the law regarding the list and the government really doesn't enforce it anyway. Then you have all the outsourced phone farms that can just ignore all of it to begin with because the US gov't can't do anything to them.
While I wouldn't put it past some of these app developers to collect numbers and sell them for profits, I also wouldn't completely dismiss it being from the do not call list. I never registered any of my numbers on the list, and have not received any telemarketing calls. With it just happening all of a sudden, it could just mean someone just happened to recently buy a list that had your number on it, and have nothing to do with the market.
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