As a part of call centers, the collections center is regarded as one of core competency of financial institutes. However, the operations of this collection centers is still relying on the accumulated experiences and knowledge based on trial and error due to very limited proceeding studies. In this study, an analysis on the proper level of collections activity in terms of calling customer in early stage of delinquency was performed by linking of system dynamics and past historic data of collection center operation. As the result of this SD simulation, optimum level of customer treatment in terms of calling intensity was obtained and over treatment above the optimum level can cause the exceeding of incurred collection expense for over treatment against the credit loss saving impact obtained by this over treatment. It is expected that this result of study can be applied to the mobile telecommunication companies where they handle early stage delinquent customer for the telecommunication bill on the top of financial institutes.