Collection agent threatened me with willful default

I have a personal loan running with IndusInd Bank and I have been paying every month, despite 6 months of me being unemployed due to medical reasons. Because of my unemployment status, the emi date is being stretched a little but I never defaulted on a single payment ever. I had recently a very small shortfall amount of around 500 rs which I promised to pay by day end and paid also. I honoured my commitment to them. The agent in between called me up, threatened me with putting my name as a willful defaulter and was very rude and threatening to me saying he will send agents to my home for recovery. It was an extremely unpleasant experience with a very rude fellow. I have a good CIBIL score still and have not done anything to warrant this action. Can I take further action on the agent and the bank? It has caused a great deal of emotional turmoil. Can I approach a court on this and serve a legal notice? I would be very thankful for guidance please.