eBay

I didnt set shipping fee high enough. But buyer agrees to pay difference and now making excuses about how hes having trouble sending $ via paypal.It was my goof but now it looks like he wants to cancel after paying for item ($300)I havent shipped yet...

Im seller and need to add another $60 to shipping cost but buyer has paid my paypal. Im new so i cant touch the money until buyer receives item. How can he add more money to the sale at this point?