ICICI Bank — Settlement of Loan not Processed by bank

This is regarding a my loan with ICICI loan no LIBNG[protected]. I had discussion for settlement with manager of ICICI and spoke for settlement for Rs 14000 in 2 installment. I paid 2000 immediately and gave a cheque for Rs12000. The gave me a receipt saying full and final settlement, and promised to send a loan closure letter in 10 to 15 days. This happened few years ago and the bank didn't process it properly and they are demanding Rs 8400 till now. several complaints to Customer care and also walked in directly didn't help. Every time I go to bank they inform they will check and get back and no one get backs to me. this has also been impacting my CIBIL scores. Kindly help me.