You are entitled to a refund only for the money that you still have in your account. We are not able to refund money that you already spent.
If you want to get a refund and withdraw the money from your account, all you have to do is transfer balance to a publisher wallet and then request a withdraw.
STEP 1: Click on your wallet balance and transfer it to a publisher wallet.
STEP 2: Request a withdraw from "Billing" section