Clearly a scam. Using an "abused dogs of law enforcement" for their scheme. A few months ago it was "vehicle warranty extensions" before that it was "free cruises for a $50 processing fee" and before that it was a "free rewards card". Sprinkle in the obligatory "prescription" drug refill calls from several hundred different robo dialed numbers that when called back lead to a "phone number is not in service" message or a busy tone and you have your persistent criminal scammers that no one wants to shut down.
I get calls like this all the time. Just like Matt said, the hundreds of different numbers they call you from often lead nowhere and their scam changes every month or so. Once they have your CC# it's over for you. If you want to donate to a charity do it yourself. You control the contact. Good luck.