Redress.
Write the problem down and pass it up the chain.
Explain what you have done about it, how much you are owed and, most importantly of all, what you want the Service to do about it. Don't make wild threats unless you are prepared to carry them out, but I don't think it would be unreasonable for you to explain that you will seek refund of interest or bank charges if these are accrued as a direct result of the failure of the system (and yes, you will need to prove it!).
It concerns me that redress seems to be considered as some sort of black mark on a career - I would have thought most of those in the chain of command (particularly unit/stn cdrs) would be happy to have evidence to support the general view that the system is not working. In this particular area, you are not redressing the Stn Cdr as a personal attack, it's just the only way to get the problem resolved!
Good luck!
STH