Is it possible to return money to the sender from a PayPal merchant account without loss?

Question

PayPal

The situation is this. I am IP. A foreign customer who has owed money for three years already (of course, neither his company nor that contract is gone), suddenly decided to pay off the debt by unexpectedly sending me money to a PayPal merchant account, which I never used in my life. The transfer was instantly converted into rubles, losing an impressive amount in the process. Is it possible now to roll back the transfer completely (and not by adding a bunch of money on my part to make up for the double conversion)? And How?