Those websites don't have my phone number.

The ads/analytics providers very well might. They gather data and cross-reference from tons of different sources.

And I don't know about you, but I've put my phone number into a lot of apps and sites. Sometimes it's required, sometimes it's for 2FA, etc.

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apparent 13 hours ago | parent [-]

I use a virtual number for almost all such signups (only doctors or other safety-related providers), so I'm not sure that would be a possible avenue for these calls, which come to my direct cell phone number. It is not quite a secret, but it is not something I give out to many companies.

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crazygringo 12 hours ago | parent [-]

They do pattern matching against lots of pieces of information. It could be as simple as a local utility company selling their customer list with phone number and address attached, then a retail website has your address from when you bought something, now your phone number gets linked.

It doesn't matter if you don't give your phone number to many companies, it only takes one.

	▲	apparent 11 hours ago \| parent [-]
		Pretty sure my doctor isn't leaking my phone number. I don't give it to companies. It's also not clear why I would have an uptick in spam calls when I'm traveling. I get 2x/week at home and 2x/day when traveling.