] accepting payments online, via card processers like Stripe, guess what ...
] fraudsters(carders) will sign up for your service/buy your digital product - to TEST the stolen credit card #'s that they have purchased, if payment goes through, card will likely be used for more fraudelent charges
] some time later (after the card owner gets theri statement with charges s/he doesnt recognize, and disputes those charges with the card company
] your pp will cancel your 'payment recieved' AND
] your pp will ADD their own additional FEE for 'cancelled payments'