Since deposits and withdrawals only ever move simulated virtual funds, there is no real payment to reverse or refund.
A deposit or withdrawal request that is still Pending has not yet affected your final balance state in a way that can't be corrected — contact Support if you'd like a pending request reviewed or reversed.
If you believe your virtual wallet balance, transaction history, or game history is incorrect due to a bug rather than the normal outcome of play, contact us through the Contact/Support page and describe what you expected to see.