Receiving payments but not allocating it.

I have just received a phone call from Andiswa, ref ***, who claims that I still owe R9518.51 on my account. HOW IS THAT POSSIBLE AFTER ME MAKING PAYMENTS EVERY DAMN MONTH????I have had it with this ridiculously poor service and allocations of payment s made into your account. At first you could not find the money that was paid at the store, then you could not find that money that was paid into your bank account… What will be the latest excuse???

I need this resolved urgently!!!!!