Bad customer service

I have been in contact with the company, trying to resolve late payment. I made a payment via ATM deposit and i forgot to put my ID number as the reference number. I have emailed the proof of payment and they promised to call me back once they have allocated the money, but this has not happened. Some of their staff have no sense of emergency at all and they are very impatient. They show no interest when you explain your problem. Once i have paid my last installment, I am done never borrowing from them EVER AGAIN!!!!!