Useless accounts department

For months now we have been battling with the accounts department. Every month I send all the proof of payments for the year and to date the payments have not been allocated. Where is this money lying?

A few of the payments have been allocated but they just cant seem to get it right. Now that the end of the year is drawing near, they send out letters threatening that my child wont be able to attend the school next year if the "outstanding" amount is not paid. Even worse, this same letter says to speak to the bursar (whom we have been dealing with for months) and ironically she happens to be on leave for a month.

Despite speaking to various people, from the bursar to the Myhub team, to the principal and head office, nothing has been sorted. Who can I turn to? Who can allocate the payments once and for all?