Payment order in status "Pending transaction - Insufficient funds! Please replenish your account!" will remain on hold until the current day's transaction processing deadline, i.e. 5.30 pm Monday to Friday and 11.30 am on Saturday, and will be processed if funds are replenished or declined if insufficient funds are received by the deadline. 

It can be cancelled via a secure message within the application, in the "Internal messages" section.