Unfair treatment by the bank

I am Nobuntu ***uthwa I borrowed a loan of R27000 and l paid it within a period of six months and l was told that l have finished paying my installments as l paid 6 thousand and 13 thousand in cash. On the 7th month they again debut the full installment and when l called them they told me they will refund me but they did not until l reversed it by myself. I was then admitted at hospital and they debited again and l could' nt be able to reverse that one. I feel that they are now treating me unfairly