You can do this right from the poker client.

  1. Log in to your poker account
  2. Click on the ‘My Account’ page on the bottom right
  3. Then click on ‘Withdrawal’
  4. Then ‘Account’
  5. Then ‘History’
  6. Click on the ‘Pending Withdrawal’
  7. Finally, click ‘Cancel’.

That’s it, your payout request has been cancelled and the money has been credited back to your poker balance.