E-mail isn't dead -- and in fact, its use is growing. Customers still use voice services as their No. 1 channel for service from a company. And customers aren't satisfied with the way companies handle service issues in online forums and on Twitter. Those are some of the findings of a recent report on multichannel customer service, and the takeaway, writes Lucy Holloway, is that companies can't focus on any one channel -- but must somehow excel at all of them. She offers six tips for making it happen.