Here’s a great article about the reality of call center call volume forecasting by James Lawther:

http://www.squawkpoint.com/2012/11/call-center-forecasting/

My favorite quote from it:

“If your forecasters were the sort of people who could precisely nail the outcome of a random, chaotic, complex system, day in and day out, then they wouldn’t be forecasting your call centre. They would be playing the euro-millions lottery for 5 minutes every Friday and spending the rest of the time cruising the shores of the Mediterranean in a Ferrari.”