Incredibly unprofessional

I don’t understand how Wonga will want a POP for a debit order. They debited the money from my account then said I must wait when I asked for the statement as it takes a while for the funds to reflect. to then saying the debit order didn’t go through and my bank cancelled it. Now I’m expected to put together some letter all because they don’t want to allocate the funds I’ve paid and close my account???? This is bad business