I think PayPal would also email you in addition to calling you if they got any issues. I got an email from them when they were hacked reminding me to change my passwords (even though my account has zelch and WAY OUTDATED info on it that people would find useless.). Few professional companies would call you anymore since they're well aware of phone scammers out there. Always a smart choice to do some research if you don't know who that caller really is but people can use fake number nowadays so it's really hard to tell. If you can't tell, then drop in a support ticket or email (to Paypal) to verify if someone has called you from Paypal or not.