PayPal Unrecognized $400 Transfer Appeared in My Account

I have no connection with PayPal and do not believe I have ever had any membership, account, or transaction with the company. Despite this, approximately two days ago, I noticed that a payment of approximately $400 had been credited to my account through PayPal. I do not know why or how this transfer was made, and I believe it occurred without my knowledge or authorization.

I have not contacted my bank yet because I am first trying to understand the source of this transaction and how it is connected to PayPal. I have also never contacted PayPal directly, as I have no relationship with the company. I want this transfer to be verified, canceled if necessary, and handled in a way that does not cause me any problems in the future.

I also do not know how to contact PayPal directly. I request that I be provided with an explanation as to why approximately $400 was sent to my account, that the transaction be investigated from a security perspective, and that it be corrected if necessary. I would also like to be informed about what steps I should take during this process.