Installment calculation

I have sent an email again regarding my installment calculations ,no one is calling me and you want to deduct R500 on a balance of 2500 which is calculated over 24months,can someone call me before my debit order goes through regarding this matter,ever since I've joined RCS I have no joy regarding your terms,last months got an email it was sorted my installment is R118 now it's R500 what is happening ,they said the loan is on 24 months now again things have changed ,I.made sure I paid R250 pushing the account,now this I don't want to be inconvenienced