Our attrition rate runs around 2.5% per month and much of that is voluntary because customer service is not for everyone. It's the kind of job that will make you or break you. Although the reps actually only work with maybe 2-3 truly difficult customers a day, many people will make personal attacks just to get under the person's skin and try to abuse the person into giving them what they want.
I admit that as a company we do have opportunities, but we take our feedback and truly consider what the customer wants. We can't always fix everything, and there is the consumer accountability peice that customers often time fail to consider. Ultimately, we will continue to improve but in the end there will always be turnover.