Kotak Mahindra trying to recovery a 10-year old that was already paid off!

Hello
I desperately need help in this topic. Now, in 2015, Kotak Mahindra has sent me a letter saying that a loan amount is pending! I have taken no loans from the bank ever and I have no paperwork, no details, and no way to verify the details. I dont know whether to contact the bank or what to do. I dont know what’s wrong with this bank.