Car Donation

Donated a car earlier this year to an "IRS approved" organization. Got a letter from organization saying car sold for more than 500 dlls.  but they want me to either send a slip that comes with this letter with my SS or to call a secure voicemail system and providing this info. Organization explaining they need SS to prepare 1098-c. Obviously don't want to give the info; really don't know what to do.