Dang, at least you're getting a response from cex.io but this isn't acceptable. Cex.io could easily claim that they are having difficulties with their payment processor, and inform their customers about the ongoing delays. Or even after they claim they sent the funds, they can say that there is something wrong with the payments that they're trying to figure out. But instead, they say the transaction is sent and doesn't follow up with anything until a complaint is filed.
We do not intend to hold customers' money for purpose as we understand that it has a negative impact on our reputation.
Unfortunately, we have currently got in the situation when the payments are processed longer than acceptable and longer than we want them to be.
We are currently looking for the better payment options. As for now, we kindly ask you to stay patient.
If this is the case, why not let the customers cancel their withdrawal requests and credit them back with their USD balances? That way they can either choose to wait for the withdrawals to be processed, or sell for bitcoin which they can cash out instantly. That is a much better solution imo.