If you have seen the phone number 402-935-7733 (or 4029357733) associated with PayPal on your credit card bill or bank statement, this is a legitimate PayPal customer service phone number.
This phone number is a reference phone number for you to call if you have questions about a particular PayPal charge, and seeing it generally means that you have either made a purchase with your PayPal account with your credit card/debit card as the funding source, or you have made a purchase with a retailer that uses PayPal as their credit card processor (perhaps an eBay seller but it could be another merchant as well).
If you’re still unsure, you can see that PayPal itself confirms that the phone number is theirs on this page of their online Help Center.