Where did they get my phone number?

There is no lookup that answers this directly. The evidence comes from the calls themselves, and from making your next sign-up traceable.

Our method, not a rule

A phone number cannot carry a tag, so log every unwanted call. Record the number, the words the recording opens with, and the number it tells you to call back. Robocallers switch caller ID numbers, but the recording and the callback number stay the same, so the log groups them into one campaign.

The FTC asks for the same details when you report: Report the number that received the call, the number on your caller ID, and any number you're told to call back. (FTC). It also says Caller ID is easy to fake, so the number on your screen may not be the caller's.

Ask a live caller

A live sales caller has to tell you who they are calling for. Ask for the company's name and where they got your number, and write the answer in the log.

Make email traceable from now on

Give each company its own tagged address, such as yourname+shoestore@gmail.com. Google: Use yourname+shopping@gmail.com to create an account with an online retailer. (Gmail Help). If spam later arrives at that address, the tag points to the company that had it. Anyone can delete a tag, so spam at your plain address proves nothing.