I think I have a simple solution for you. Those who use contabo will understand this. So Contabo has recently started to announce their charges to paypal. the email reads, 'you have opted for automatic charges and your paypal will be charged $x.xx in 10 days. This is a brilliant move in my opinion and quite trivial to implement. You give the customer ample time to investigate any errors and/or challenge or change settings/cancel. I think most companies don't like to make "cancel process" too accessible but that's no way to treat customers man.