Spikes in retail traffic

Hello,

Does anyone have any ideas as to how to cope with possible spikes in calls. Forecasting fails if the half hourly call pattern is not random. Our MIS will go down to 15min intervals but I’m not sure if this will be too detailed for forecasting Calls per day and the daily call pattern. Any thoughts would be appreciated, esp from someone who deals with calls from agents who deal with the public (high street customers).