No Access to a customers email address that has made a payment to me through PayPal.

Description

I want to send an eBay customer a partial refund on over quoted postage, but no access to their email address anymore? Why? It used to be on the invoice. What has happened? I have their phone number from eBay but it appears that it is not registered with Paypal. Another situation is that I want to invoice someone for extra postage on an item, I have their name address and phone number but cannot send an invoice without the email address?? Crazy.. Also the support is non existent atm. I cannot believe the lack of support.