You phone number must have reached them in some way (maybe sending a few bucks to them, or bought something like survival rations). Once there, it spreads like a virus. Best option, although quite painful, is to get a new phone number and protect it better (give out fake numbers except where it counts). I do that in doctors’ offices with my SS number, as they only use it for deadbeats, and since I pay my bills, its never given me a problem (obviously I keep the fake number close enough to my number to be able to claim ‘a mistake’ if ever challenged)
Other than a new number and some of the ideas above, I too wouldn’t come up with much.
I just skip that question. Never been asked about it.