How to reduce fraudulent PayPal payments?

Hello everyone.
In summary, we receive credit / debit card payments stolen for the purchase of our online services. When the cardholder understands what is happening, PayPal puts the money on hold and we have no chance.
We begin to reimburse payments and even after reimbursement (which even has a 5% loss) we sometimes get rebate rates of $ 20!
Can anyone give some ideas to avoid this? The proportion of real payments / fraud is 50/50, which greatly reduces our profits …
Any ideas?

Thank you