I logged into my PayPal account, then used the "Contact Us" link that was with other links at the bottom of the page.
That led to a page that included a "Call Us" link that led to a page with a toll-free phone number, and giving me a "secure Web PIN", supposedly good for one hour.

The phone number they give you may depend on the type of account you have. I've read that personal accounts don't get toll-free numbers.

Here's an eBay thread that claims to have some phone numbers. The toll-free number I saw at PayPal matches one of the numbers shown in that thread; I can't personally vouch for the accuracy of the others.

Question: When you logged onto your PayPal account, was there a transaction shown there that would correspond to the charge?