Action against Tenant for not giving additional security deposit

We are a co-operative Society & have rented our premises @ Rs 100,000 per month to a Nationalised Bank for 10 years starting 1-1-2012. As per written Agreement, rent will increase by 10% after 5 years from the start of the agreement. As per one of the clause, tenant is required to pay 6 months rent as security deposit. So as on 1-1-2012 Tenant paid the 6 month deposit of Rs 60,000. Although Tenant has paid increased rent of Rs 110,000 per month from 1-1-2017, he did not paid additional Security Deposit based on increase in rent from 1-1-2017 calculated at Rs 60,000(new deposit 660,000 - old 600,000. We have sent written communication to Tenant on 1-1-2019 that the additional deposit of Rs 6,000 was payable as on 1-1-2017 and hence requested then to pay additional deposit of Rs 6,000 along with interest for the period 1-1-2017 till date. The Tenant has paid the Deposit on [deleted] but refusing to pay interest. Note that the agreement does state that Society has to give notice to Tenant for paying additional deposit. What are options available to us? Can we go to Banking ombudsman ? or any other recourse available to us?