Should blocking calls always be avoided, or are there times when it's acceptable? Can blocking help even out peaks in call volume?
Blocking calls is acceptable in some circumstances. The easiest example is extreme peaks, such as "Tickets for Springsteen go on sale at 10 a.m. on Saturday!" In these cases, callers don't expect that they will get through every time, and it would be very difficult and expensive for the call center to have trunking and staff to meet that peak demand. Another example is some call centers will use blocking to prevent callers from accessing their center when they would just sit in queue for a long time, hoping that the busy signal will serve as a deterrent to calling during the busiest times and encourage callers to call at another time. Other call centers prefer to let the callers in and provide a message indicating it is the busiest time, providing an expected wait time, or offering the option to leave a message for call back; all of these options can also help flatten peaks while giving the callers access and choices.
So yes, call blocking can help even out peaks, but you need to assess your callers and their expectations, your competition, your business strategy, your other performance characteristics and other factors about your products and services to determine if it's the best strategy for your call center.