Once you have initiated a withdrawal, the transaction is automatically created and sent to the blockchain. Please give it a few minutes to get confirmed by miners. We cannot expedite this process as it depends on the current network load.
If you decide not to withdraw the funds, you can cancel the transaction if it has not yet been sent to the blockchain (i.e. it has not been assigned a transaction hash).
If this option is not available, it means that the transaction has already been sent to the blockchain and is currently being processed.