Finding this information on the PayPal website is quite tricky and some users have suggested this may be because they prefer receiving requests by email and want to reduce the number of calls. You can contact PayPal customer service at the toll-free contact numbers below:

Toll Free for Business/Premier, USA & Canada: 1-888-221-1161 / 1-888-204-4481

Personal Accounts: 1-402-935-2050

PayPal UK: 0870 7307 191

They are open between the following hours:
4:00 AM PDT to 10:00 PM PDT Monday through Friday
6:00 AM PDT to 8:00 PM PDT on Saturday and Sunday