Regarding non payment of bills of the society

Hi. I need help for the below questions as where to approach for the regarding matter . We are a co-operative society formed since last four years . As last two years we are facing some problems from 6 to 7 tenants who are refusing to pay their maintainence bills . We approached the SRA with the complaint as they have ordered us with the letter to proceed that we can file case on that members those doing so. So can anyone guide what will be the best to do now. Please let me know.. Sandeep. M. Pawar