: In this paper, we consider the customer call center operation which is one of the personal computer enduser services. We deal with the problem as a case study where the optimal allocation of the call center staff which is called agents is determined. This previous proposed model was to provide the optimal agents' allocation for the call center service based on queuing (Erlang loss formula) [18,19] and linear programming theory [20]. Here, besides it, we're going to address or examine the mode, considering the queuing space of not-using phones or the phones that no agents are using and the repeated calls that the customers would call when they couldn't reach any agents directly or immediately, and they couldn't even get into the queuing space of not-using phones. Then we show the effectiveness or the extent of the effectiveness of the model.