In the literature on service facility system, it is common to assume fixed service rate, such as flexible retrial arrival, this assumption is not realistic. In contrast retrial demands model rarely define the mechanism through which arrival of customers is classified into two types say priority customers and ordinary customers. For the given values of maximum inventory, maximum waiting space, reorder level and lead times, we determine the optimal ordering policy at various instants of time. The system is formulated as a Semi-Markov Decision Process and the optimum policy to be employed is found using linear programming method. Numerical examples are provided to illustrate the model.