I used to get calls for the Policemen's Benevolent Society, or something like that and also from the Illinois State Police for their charity. This was back when we had a land line and caller ID, so I knew the calls were legitimate.
Read up on those calls and you'll learn they are almost invariably a scam. Police organizations do indeed sign up with the fundraising companies, but those companies then use huge boiler room operations, often out-of-state, to make the calls. Some even manipulate phone numbers to appear legit on caller ID.
Then, a tiny, microscopic fraction of the often huge sums raised actually go to the police groups. Even that sliver of the actual take is more than nothing, and the effort required from the police groups is zero, so they continue to sign up.