We consider a stochastic staffing problem with uncertain arrival rates. The objective is to minimize the total cost of agents under some chance constraints, defined over the randomness of the service level in a given time period. In the first stage, an initial staffing must be determined in advance based on imperfect forecast of the arrival rates. At a later time, when the forecast becomes more accurate, this staffing can be corrected with recourse actions, by adding or removing agents at the price of some penalty costs. We present a method that combines simulation, mixed integer programming, and cut generation to solve this problem.