So I don't find it at all difficult to believe that our OP could somehow, in cyberspace, be connected to the person who actually owes the bills without him being actually connected.
Yes, we all know that lots of information about people, their various names, telephone numbers, relatives, friends, blah blah, can be easily found - and much of it is old or just plain wrong information. But the OP's situation is not as simple as that, and using this thread to discuss all of the various ways that debt collectors CAN find information and all of the various ways that debt collectors CAN try to find and pressure the debtor, misses the point about the OP and THIS thread.
I think Zinger summarized the OP's post best: Let's say that DiverDan doesn't pay his bills. The bill collectors got FlyingRon's phone number connected to DiverDan somehow and call (a lot), including using spoofed numbers. In response, FlyingRon changes his phone number. Shortly thereafter, the bill collectors start to call FlyingRon's new number asking for DiverDan, so he changes it again. Shortly afterwards, the collectors start calling FlyingRon asking for DiverDan AGAIN, including using spoofed numbers that, coincidentally, belong to relatives of FlyingRon.
The second sentence of Zinger's summary would not surprise me at all. But a debt collector who calls new numbers that the OP received, and spoofs CID numbers of relatives of the OP, all while looking for someone totally unrelated to the OP or the OP's relatives, well, that just seems unlikely to me. Possible, sure. Likely, not.