Allocation of payments

I am very much angry with Holiday Access, the timeShare company based in Durban. I had problems in paying and eventually the debit order was cancelled, then after months of paying to the correct account with the correct referrence number, i sent an email to them asking how much the balance was, and was told that i must send all the proof of payments, but they have seen all payments yet they were not crediting my account. The account is accumulating interest unnecesarily.